An explosion at a historic Texas hotel in Fort Worth on Monday blew out windows, littered downtown streets with large piles of debris from the building and injured 11 people, including one person who is in critical condition, authorities said. Investigators believe the blast was caused by natural gas, said Bureau of Alcohol, Tobacco, Firearms and Explosives spokesperson Sara Abel, who was briefed by local police. Two people were in serious condition and the rest had minor injuries, authorities said at a news conference.

Medics also treated four more people on the scene but did not take them to a hospital, said Desiree Partain of MedStar, which provides ambulance and emergency medical services in Fort Worth. The Sandman Signature Hotel is in a busy area of downtown about one block from the Fort Worth Convention Center. Footage from news helicopters showed firefighters picking their way through the piles of drywall, shattered glass and mangled metal that coated the street outside the hotel. Authorities urged people to avoid the area.