Flights in and out of New York's John F. Kennedy International Airport are back on schedule after a false gunman scare last night led to evacuations and a four-hour sweep of two terminals.

Passengers at New York's John F. Kennedy International Airport were told to take cover behind 'anything' they could find by police on Sunday night - as unfounded reports of gunfire in Terminal 8 caused mass panic.

Every passenger was evacuated from the terminal, some onto the runway, as an army of heavily armed police moved in to hunt for an apparently non-existent gunman.

One passenger said an officer screamed: 'If you're forgetting anything it's not worth your life, everyone move now!'

Flights were grounded and authorities spent four hours searching the terminal - as well as Terminal 1 - where there was also a report of gunfire.

But the scare turned out to be a false alarm, with one theory speculating that 'cheering' for Usain Bolt's victory in the 100m final may have been misinterpreted as gunfire.

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Police evacuated Terminals 1 and 8 at New York's John F. Kennedy International Airport out of an 'abundance of caution' following reports of gunfire

A Twitter user posted this picture, writing: 'On a plane at #JFK and a bunch of people just ran out on the tarmac'

Police evacuated Terminal 8 around 9.30pm on Sunday as a precaution after receiving reports of shots fired near the departures area.

Officers from the New York Police Department were called in to assist with the investigation.

A short time later, police closed Terminal 1 after they said they received additional reports of shots fired in that terminal. The Van Wyck Expressway approaching the airport also was shut down.

According to the flight tracking company, FlightAware, all inbound flights were held at their origin until 11.30pm 'due to security.'

Police later said they had evacuated Terminal 8 out of an 'abundance of caution' following reports of gunfire, but say investigators found no evidence of shots fired.

Port Authority police said travelers should contact their carriers and warned of a 'substantial PAPD and NYPD presence' at JFK and LaGuardia due to the investigation.

No one was injured during the airport scare.

A terrifying video, uploaded to social media by Barcelona-native Albert Salas, also emerged of the moment armed police stormed through the airport.

Passengers can be seen hiding behind chairs and screaming as heavily-armed police cleared the terminal.

In a statement, the Port Authority of New York and New Jersey said: 'Preliminary investigation does not indicate shots were fired at JFK.

'At this time, no gun shells or other evidence of shots fired has been found. The terminal was evacuated out of an abundance of caution.'

The NYPD Special Ops account tweeted officers 'are clearing Terminal 1 & 8 (Departures). There is nobody shot. It appears that no shots have been fired.'

They later added: 'All terminals searched & cleared. Negative results. All affected terminals will resume operations shortly. No shots were fired.'

Police evacuated Terminal 8 around 9.30pm on Sunday as a precaution after receiving reports of shots fired near the departures area

Terminals 1 and 8, as well as the Van Wyck Expressway approaching JFK Airport have all been closed as a safety precaution

Thousands of passengers were forced to evacuate the terminal shortly after 9.30pm

The NYPD Special Ops posted these pictures on Twitter, adding: 'All terminals searched & cleared. Negative results. All affected terminals will resume operations shortly. No shots were fired'

The panic began after a woman coming off a plane said she thought she heard gunfire, a law enforcement official told NBC News.

But police believe 'cheering, clapping and banging' from people watching the Olympic Games may have been misinterpreted as a fight and gunshots - as Jamaican Olympian Usain Bolt sprinted to victory in the 100m final shortly before 9.00pm

Demetrius Pipkin, who was inside Terminal 8 at the time, told PIX11: 'We were previously told to get on the floor and take cover behind any and everything we could find.'

He said the place was a 'madhouse' as travelers looked for an escape, but found none.

'When we finally were able to find exits it led to the runway, which is not necessarily the safest place either,' he said.

By around 11pm, he said security staff were trying to reunite lost children separated from their parents during the mayhem.

Pictures posted on Twitter appeared to back up Pipkin's comments.

Josef Pfeiffer posted a picture, captioned: 'On a plane at #JFK and a bunch of people just ran out on the tarmac.'

Joshi Herrmann posted on Twitter that he was in the terminal about to board a flight bound for London when 'suddenly everyone in Terminal 1 sprinted in my direction, along the corridor of gates.'

He added that he and five others hid in the cupboard of the Alitalia lounge 'for about half an hour, or it felt like that.'

Armed police searched for an alleged armed suspect on Sunday evening after the reports

'Outside we saw hundreds of people sprinting away from the terminal building and lying for cover behind vans. Inside it was totally quiet,' he wrote.

'I didn't hear any shots, beyond the noises of people sprinting in all directions. No one I've spoken to says they did either.

'That was a high grade panic.'

Armed police just came and let us out of the cupboard and led us out of Terminal 1 where tons of people are waiting.'

Dan Archer, who was in the terminal at the time, reported 'panic' as gates were closed at security due to a 'possible shooter.'

'Still not confirmed shooter police armed and patrolling we're still in security by screening with gates locked down,' he said on Twitter.

Passengers were left stranded on the street after the whole of Terminal 8 was evacuated

Terminals 1 and the Van Wyck Expressway approaching JFK Airport was also closed as a safety precaution

The Port Authority of New York and New Jersey said no evidence of gunfire was found but the evacuation was out of an 'abundance of caution

Police are responding to reports of shots being fired inside JFK Airport's Terminal 8

A massive police response has begun at the airport, in Queens, on Sunday evening

Pictures posted on social media showed huge crowds of people evacuating the terminal

He added later: 'We're all safe, collecting belongings, been told the situation has been cleared at #jfk'

'Police won't say anything except "it's not safe to stay here" as we leave terminal 8.'

Robbie Rob added: 'Everyone is being kicked out of the terminal. Police on alert!'

Some passengers on social media reported flights due to land at JFK were being diverted without crew informing them why.

'About to land at JFK, but pilot suddenly announces flight diverted to Buffalo! JFK apparently 'shut-down'. No idea why,' wrote Umang Dua on Twitter.

Laura Reddy, 28, was on a flight from Hong Kong that was due to to land at Terminal 7 at around 10.40pm.

But she told Daily Mail Online that the pilot announced that the flight would be held at the runway for at least an hour 'due to a shortage of staff inside the airport because they had to evacuate.'

Robbie Rob said on Twitter: 'Everyone is being kicked out of the terminal. Police on alert!'

'Police won't say anything except 'it's not safe to stay here' as we leave terminal 8,' one person wrote on Twitter

No injuries have been reported and no other details were immediately available