(Part-2) Historic Texas hotel explosion injures 21 and scatters debris in downtown Fort Worth.

A UPS driver named Paula Snider was making a pickup when she reported hearing a loud boom and seeing a cloud of dark smoke. Under her truck, a big chunk of metal grating fell, and another one fell close by. "I leaped out and ran away," she said.

As firemen combed amid piles of rubble, a cloud of gray engulfed the usually bustling streets of downtown Fort Worth. There were pieces of the structure lying around on the street and on top of parked cars, and there were holes in the ground.

According to Trojacek, local and federal authorities are collaborating to find out what set off the explosion. Rescue workers were delayed in their attempts to access some areas of the structure due to the chaotic atmosphere.

After the explosion, "some of those access areas were either covered up or it didn't feel safe to get people down into the basement," according to Trojacek, who said that there were reports of individuals stuck there.

Atmos Energy, a natural gas distributor located in Dallas, sent technicians to investigate the explosion site on Monday. According to a representative from the Railroad Commission of Texas, who is responsible for regulating the oil and gas industry in the state, an inspector from their agency is also there and assisting local authorities.

Officials are collaborating with Northland Properties Co., a Canadian firm that owns the hotel, to ascertain the source and extent of the explosion, according to a statement.

"Our top concern is ensuring the safety and welfare of our employees and customers," the business stated. "We are actively assisting the injured in providing them with full support during this difficult time."

Built in 1920 as the "Waggoner Building," named after cattle rancher and oilman William Thomas Waggoner, the Sandman Signature Fort Worth Downtown Hotel possesses 245 rooms, as stated on the hotel's website. In 1979, the structure was added to the National Register of Historic Places