Fort Worth, Texas - Twenty-one people were injured after a suspected gas leak caused an explosion on Monday afternoon at the Sandman Signature Hotel building in downtown Fort Worth, Texas, US officials said.

One person was in critical condition, four were in serious condition, and the remaining people suffered minor injuries, according to MedStar spokesperson Matt Zavadsky. No fatalities were reported.

A person who was unaccounted for earlier in the afternoon was later found, Fort Worth fire spokesperson Craig Trojacek said at a news conference. According to Trojacek, several people had to be extracted from the hotel’s basement, which also features a restaurant, Musume.

The explosion occurred during ongoing construction inside the Asian fusion eatery, Trojacek said. The cause of the explosion has not been confirmed, but officials believe it may have stemmed from a gas leak.

Witnesses, even those blocks away from the building, described a rumble so loud and sudden they thought it was an earthquake. The putrid smell of gas, akin to rotten eggs, lingered in the air long after dozens of patrol cars and firetrucks arrived.

Pieces and panels of wood, glass, and drywall were strewn across a two-block radius, and a section of a wall ripped from the building was propped up on a tree near the sidewalk, some of its windows still intact. In other places, window frames dangled from outside walls.

The hotel, and some surrounding buildings, were evacuated. Trojacek said 26 rooms were occupied in the hotel at the time of explosion.

"It was chaos for a minute there," Trojacek said about the scene when first responders arrived.

Governor Greg Abbott said in a statement that state officials were staying in close contact with local leaders, partners, and first responders to help with emergency response efforts. He said officials were continually monitoring the situation and "stand ready to immediately deploy any additional personnel and resources" to keep residents safe.

Fort Worth Mayor Mattie Parker said her heart and prayers are with those injured, calling the explosion a "heartbreaking incident for the city" and for the recently renovated historic building.

"All of us at Musume are devastated by the tragic explosion that took place this afternoon," Josh Babb, owner of Musume, said in a statement sent to The Dallas Morning News. "Luckily, Musume was closed during the time of the explosion, so we had no customers dining and limited employees working."

Babb said three restaurant employees were injured but stable Monday evening.