An explosion Monday afternoon at a historic hotel in downtown Fort Worth, TX, which preliminary reports said was caused by natural gas, injured at least 21 people, but no fatalities had been reported as of early Tuesday, authorities said. 

The blast occurred at the Sandman Hotel in the heart of the business district downtown.

Multiple 911 calls were received at about 3:32 p.m. CT Monday for a fire at the hotel, said Fort Worth Fire Department (FWFD) spokesperson Craig Trojacek. Authorities once on the scene switched the emergency to an explosion.

One person was said to be in critical condition.

Crews from Atmos Energy Corp., the natural gas utility that serves the area, were on the scene as well, Trojacek added.

“We have not made 100% determination, but we wanted to...