A blown transformer knocked out power to part of the Hilton New York Hotel on Sixth Avenue Wednesday afternoon, trapping some people in elevators and causing smoky conditions, officials said.

Many guests in upper floors walked down dozens of flights of stairs to evacuate the building. Three people suffered injuries that were not life-threatening, officials said.

All of the people stuck in elevators were rescued, officials said.

The transformer, in a sub-basement of the hotel, crackled and exploded with one large boom and then shorter bursts, according to witnesses.

The explosion “sounded like gunfire,” said Mark Parrell, who was attending a conference at the hotel.

Guests staying on upper floors said they didn’t hear the explosion, and only noticed their lights went dark.

“Everything just went out,” said Erin Salstrom, a guest visiting from Minnesota. She said guests on floors 4 to 44 were told they didn’t have to evacuate, but she and her husband decided to walk down the 26 flights anyway.

(Source: NBC New York)