By Ruthy Munoz

HOUSTON (Reuters) - Police swarmed a Houston hospital on Tuesday after reports of a shooting but found no evidence any weapon had been fired and said no one was injured in the incident.

Police said they had received multiple calls about a shooter on the second floor of Ben Taub Hospital, a major healthcare centre in the city. They then conducted a floor-by-floor sweep.

"We have not found any evidence of a shooter yet," Houston Police Chief Art Acevedo told reporters outside the hospital. "We have not found anyone injured. We have not found a suspect."

He added there were multiple witnesses who said they heard two large bangs and someone yell "drop the gun."

He added: "I can’t say that there was no shooting. If there was a threat, that threat is not present here now."

The hospital has returned to normal operations, he said, adding SWAT officers will stay for several hours as a precaution.

Live aerial coverage from Houston television station KHOU showed officers outside the facility, with several drawing their weapons, and patients on gurneys being wheeled out.

James and Alma Delacruz were in the hospital's emergency room when panic set in on reports of the shooter. Staff blocked some doors with furniture and tried to remove patients through others, they said.

"I was really scared," Alma Delacruz said.

(Reporting by Ruthy Munoz in Houston and Jon Herskovitz in Austin; Editing by James Dalgleish)