It could take a while to learn the cause of a hot air balloon explosion that killed 19 people in Egypt this week.

An official investigation into Tuesday's accident - the world's deadliest hot air balloon accident in at least 20 years - could take two weeks, the governor of Luxor province said Wednesday.

Preliminary investigations confirmed no foul play was involved when gas canisters aboard the balloon exploded, causing it to plummet about 1,000 feet (300 meters) to the ground, Gov. Ezzat Saad said.