Police in Houston said that earlier reports on Tuesday of an active shooter inside a hospital turned out to be false alarm.

Authorities gave the 'all clear' signal about two hours after they were summoned to Ben Taub Hospital at Houston's Texas Medical Center by witnesses who said there was an active shooter, according to The Houston Chronicle.

Earlier on Tuesday, officers were reportedly said to have 'cornered' a man believed to be holding a gun.

Law enforcement sources said that a suspicious man believed by some to be a gunman was barricaded and isolated on the third floor of the hospital.

'There is an active shooter situation,' an unidentified law enforcement official said earlier on Tuesday.

But as officers were scouring the hospital 'floor by floor,' Houston's chief of police said that there was no conclusive evidence there was a shooter.

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Police swarmed Ben Taub Hospital shortly after 2pm Tuesday after reports of gunfire

Television images from helicopters show dozens of employees leaving the hospital

Officers and a SWAT team were responding to the scene in Houston

Art Acevedo, the police chief, said that law enforcement officials did their job by responding even though the reports turned out to be false.

'It wasn't a mistake, there was a specific reason (we responded),' Acevedo said.

'We had multiple witnesses that heard a man yell, "Drop the gun, drop the gun".'

'Multiple people heard two large bangs, whether or not those were gunshots is subject to further investigation.'

'We have not found any evidence of a shooter yet,' he 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 police chief said earlier that no victims had been located.

After two large-scale sweeps of the hospital, including floor-to-floor searches, officers concluded that there was no shooting.

'All patients and employees are safe at this point,' Acevedo said.

Earlier on Tuesday, Houston police spokesman Kese Smith said authorities began receiving reports of a gunman inside the hospital shortly after 2pm Tuesday.

But as police, SWAT teams, and K9 units descended on the area, it was becoming increasingly clear that there were no gunshot victims.

Officers also did not notice any of the classic hallmarks of shootings, like bullet casings, shards of glass, broken windows, or bullet holes.

People are seen walking away from the hospital as police responded to reports of a shooter

Patients in the emergency room said that initially the chaos was thought to be part of a drill, but that nurses began to disconnect them from IVs

One hospital employee said that she was in the middle of just her second day on the job when she heard a 'code white' announced on the loudspeaker

Art Acevedo (above), the police chief, says that thus far no victims have been located. 'All patients and employees are safe at this point,' Acevedo said

Smith says officers and a SWAT team were responding to the scene at Ben Taub Hospital, one of the hospitals that's part of the Medical Center.

Ben Taub is one of the major trauma centers in Houston.

Barbara Mushinski, who has worked at Ben Taub as a nurse for nine years, said that she was told by colleagues on the second floor that they heard gunshots and that someone was told to put down a gun.

The noises which resembled gunshots apparently came from eye clinic on the second floor, which is usually noisy area.

She said that 10 people who work near the clinic were immediately told to take shelter.

'It was completely unreal, terrifying actually,' Mushinski said. 'This doesn't happen all the time.'

She said that this was the third time in nine years that she had experienced a false alarm of this nature.

Television images from helicopters show dozens of employees leaving the hospital.

Some are attending to patients who appear to have been evacuated on gurneys.

In total, three patients were transported by ambulance to other area hospitals, according to the Chronicle.

Medical workers in the hospital began to barricade themselves inside offices and areas once police began to respond, according to the Chronicle.

Patients in the emergency room said that initially the chaos was thought to be part of a drill, but that nurses began to disconnect them from IVs.

One hospital employee, a student at Texas Southern University, said that she was in the middle of just her second day on the job when she heard a 'code white' announced on the loudspeaker.

'I didn't know what code white meant, but we knew we needed to lock ourselves in a room,' Pegah Nassiri said.

Nassiri said she and another student had locked themselves in a room on the first floor for 15 minutes before police found them and told them to leave.