Authorities in North Central Texas continued to investigate Tuesday morning after an apparent gas leak caused an explosion at a hotel that sent nearly two dozen people to area hospitals.

The blast took place at the Sandman Signature Fort Worth Downtown Hotel just before 3:30 p.m. local time, Fort Worth Fire Department spokesman Craig Trojacek said.

Of the 21 injured, Trojacek said, four people suffered serious injuries and one person suffered critical injuries. Their updated conditions were not immediately available Tuesday morning.

The other victims suffered minor injuries, officials said.

The hotel is about a block northwest of the Fort Worth Convention Center and photos of the explosion captured windows blown out and debris scattered across streets surrounding the business.

No longer a safety threat

As of Tuesday the blast no longer posed a public safety issues in the area, officials said.

But crews remained to continue search efforts and ensure no one was trapped.

At least one evening photo shows an ATF agent surveying the hotel's back entrance.

Photos taken after dawn show first responders still on scene among rubble, with smoke rising from debris in some areas.

Hotel temporarily closed

Sandman Hotel in Fort Worth said Monday that due to damage from the blast, it won't be taking bookings “until further notice.” 

The hotel did not immediately return USA TODAY’s request for comment.

Official origin, cause of blast remains under investigation

The official origin and cause of the blast remained under investigation Tuesday, but Trojacek said investigators believe the blast was "some kind of gas explosion."

When first responders arrived on scene, he said, the smell of gas permeated throughout downtown.

At the time of the explosion, a restaurant in the building was under construction, Trojacek said, but noted it was not definitive that is where the blast occurred.

Kristin Goodspeed, a spokesperson for natural gas provider Atmos Energy, told USA TODAY technicians were on the scene at the request of the city’s fire department.

"Gas has been isolated to the affected area, and we will continue to assist the Fort Worth Fire and Police Departments and all officials in support of their investigation," Goodspeed said.

Contributing: Minnah Arshad

Natalie Neysa Alund is a senior reporter for USA TODAY. Reach her at [email protected] and follow her on X @nataliealund.