At least 27 miners remained missing after an underground explosion on New Zealand's west coast, company officials said Friday.

Two miners emerged from the the Pike River coal mine in Atarau, located about 90 miles northwest of Christchurch, with moderate injuries, authorities said.

No fatalities have yet been reported, but concerns over ventilation at the mine has delayed a rescue effort. A power outage might have compromised ventilation inside the mine.

"They're itching to get in there and start looking for other people and a bit frustrated at having to stand and wait," police spokeswoman Barbara Dunn said.

TV New Zealand reported that Prime Minister John Key has said the situation could be very serious and pledged "any support that is required." The Australian government has also offered support, he said.

Initial reports indicated that 27 miners remained trapped in the mine, but TV New Zealand, citing a local official, said 28 remained unaccounted for.

"It is absolutely awful," Pike River CEO Peter Whittall told TV New Zealand. "At the moment, our real focus is on our people down there."

The cause of the explosion remained unknown.

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