One person was killed and three others are missing after a Hard Rock Hotel under construction in downtown New Orleans collapsed without warning Saturday morning, Oct. 12.

The city’s fire department and emergency medical services and the police responded to the scene just after 9 a.m.

One person was pronounced dead at the site and at least 18 other people were treated for injuries, a fire official said during a news conference, according to WWL-TV.

“It’s a very dangerous situation,” Fire Superintendent Timothy McConnell said, adding that the top six floors of the building collapsed and that the rest of the construction is “unstable,” and another collapse is possible.

“This remains a very fluid and very dangerous situation, and every few minutes something is falling off of this building,” Louisiana Gov. John Bel Edwards said.

The New Orleans Fire Department posted photos on Twitter showing the roof and several floors partially destroyed with a large pile of debris scattered on the street below.

The cause wasn’t immediately known.

The Hard Rock Hotel was planned as an 18-story building with 350 rooms and condominiums. It was expected to open this spring.