Editor's note: Quazi Mohammad Rezwanul Ahsan Nafis, a 21-year-old man, has been arrested on suspicion of planning to blow up the Federal Reserve Bank of New York, federal officials said. Authorities say he attempted to detonate what he believed was a 1,000-pound bomb. Below are major developments as we received them. Read the full story here.

[Posted at 6:06 p.m. ET] Nafis, wearing street clothes and represented by a public defender, was arraigned a little while ago during a five-minute hearing in a New York courtroom. No bail application has been made. Prosecutors will have 30 days to officially indict him.

The public defender said she would not comment to reporters. Nafis will be held for now at the Metropolitan Detention Center in Brooklyn, U.S. attorneys say.

[Posted at 4:18 p.m. ET] Paul J. Browne, deputy commissioner of the New York City Police Department, released the following statement on the alleged plot:

"Whether al -Qaeda operatives like (2003 Brooklyn Bridge suspect) Iyman Faris or those inspired by them like (2011 suspect in bomb-making case) Jose Pimentel, terrorists have tried time and again to make New York City their killing field. We're up to 15 plots and counting since 9/11, with the Federal Reserve now added to a list of iconic targets that previously included the Brooklyn Bridge, the New York Stock Exchange, and Citicorp Center.

After 11 years without a successful attack, it's understanding if the public becomes complacent. But that's a luxury law enforcement can't afford.

Vigilance is our watchword now and into the foreseeable future. That's why we have over 1,000 police officers assigned to counter-terrorism duties every day, and why we built the Domain Awareness System. I want to commend the NYPD detectives and FBI agents of the Joint Terrorist Task Force for the work they did in the case and in other ways every day to help New York City safe from terrorists."

[Posted at 4:08 p.m. ET] U.S. Attorney Loretta E. Lynch from the Eastern District of New York made the following statement regarding the alleged terror plot attack:

"As alleged in the complaint, the defendant came to this country intent on conducting a terrorist attack on U.S. soil and worked with single-minded determination to carry out his plan.

The defendant thought he was striking a blow to the American economy. He thought he was directing confederates and fellow believers. At every turn, he was wrong, and his extensive efforts to strike at the heart of the nation’s financial system were foiled by effective law enforcement.

We will use all of the tools at our disposal to stop any such attack before it can occur. We are committed to protecting the safety of all Americans, including the hundreds of thousands who work in New York’s financial district.

I would like to thank our partners at the FBI, NYPD, the other agencies who participate in the JTTF, and the Department of Justice’s National Security Division, for their hard work on this important investigation. I would also like to thank the security teams at the New York Federal Reserve Bank and the New York Stock Exchange for their assistance."

[Posted at 4:08 p.m. ET] Nafis appeared to have had a back-up plan.

He met an undercover agent that supplied him with what he thought were explosives on Wednesday morning. After meeting up, they both traveled in a van to a warehouse, the Justice Department said.

That’s apparently when Nafis told the agent he had a "Plan B."

If Nafis felt his attack was about to be thwarted by cops, he would invoke the back-up plan, which involved a suicide bombing operation, the criminal complaint alleges.

When the pair arrived at the warehouse, Nafis began putting together what he thought was a 1,000-pound bomb inside the van. Then they drove together to the target: The New York Federal Reserve Bank. As they drove, he armed the purported by putting together the detonator and the explosives, the criminal complaint says.

The van was then parked next to the bank. The pair went to a nearby hotel, where Nafis apparently recorded a video statement meant to be shown to the American public in connection with the attack.

"We will not stop until we attain victory or martyrdom," he said, according to the criminal complaint.

He then tried, several times unsuccessfully, to detonate the device, which was actually inert explosives.

Nafis was then arrested.

A good portion of the sting operation was caught on tape, according to a source familiar with the investigation.

[Posted at 3:59 p.m. ET] The plot came to light as an FBI undercover agent posed as an al-Qaeda facilitator, federal authorities say.

Nafis asked the undercover agent for 50-pound bags of what he thought were explosives, and then worked on putting together an explosive device, according to prosecutors.

"Nafis purchased components for the bomb’s detonator and conducted surveillance for his attack on multiple occasions in New York City’s financial district in lower Manhattan," a Justice Department press release describing the criminal complaint said. “Throughout his interactions with the undercover agent, Nafis repeatedly asserted that the plan was his own and was the reason he had come to the United States."

[Posted at 3:56 p.m. ET] We now have some more detail about the plot to blow up the reserve bank from a press release that breaks down the criminal complaint filed against Quazi Mohammad Rezwanul Ahsan Nafis:

The Bangladeshi national allegedly came to the United States in January to carry out a terror attack on U.S. soil and said he had overseas connections to al-Qaeda. As he attempted to recruit others to join his cell, he tried to recruit someone who turned out to be an FBI source, the criminal complaint says.

Nafis initially had a few targets in mind, according to the complaint, including  "a high-ranking U.S. official and the New York Stock Exchange." In the end, Nafis settled on the New York Federal Reserve Bank, federal officials said.

"In a written statement intended to claim responsibility for the terrorist bombing of the Federal Reserve Bank on behalf of al-Qaeda, Nafis wrote that he wanted to 'destroy America' and that he believed the most efficient way to accomplish this goal was to target America’s economy," the Justice Department press release said. "In this statement, Nafis also included quotations from 'our beloved Sheikh Osama bin Laden' to justify the fact that Nafis expected that the attack would involve the killing of women and children."

The "explosives that he allegedly sought and attempted to use had been rendered inoperable by law enforcement and posed no threat to the public," according to a statement from U.S. Attorney Loretta E. Lynch.

[Posted at 3:41 p.m. ET] Quazi Mohammad Rezwanul Ahsan Nafis, 21, was arrested for allegedly attempting to detonate what he thought was a 1,000-pound bomb at the Federal Reserve Bank of New York in Manhattan, the Department of Justice and a U.S. attorney's office said in a press release.

He will be charged with attempting to use a weapon of mass destruction and attempting to provide material support to al-Qaeda, the press release said.

[Posted at 3: 40 p.m. ET] A man has been arrested for planning to blow up the Federal Reserve Bank of New York, according to a federal law enforcement source with knowledge of the investigation.

The man was arrested as part of a string operation conducted by the FBI and NYPD as part of the Joint Terrorism Task Force, a federal law enforcement source said.

"Attempting to destroy a landmark building and kill or maim untold numbers of innocent bystanders is about as serious as the imagination can conjure. The defendant faces appropriately severe consequences," FBI Acting Assistant Director Mary Galligan said in a statement. "It is important to emphasize that the public was never at risk in this case, because two of the defendant’s ‘accomplices’ were actually an FBI source and an FBI undercover agent. The FBI continues to place the highest priority on preventing acts of terrorism."