Two people have been stabbed after an argument broke out between kitchen staff at Sony Music’s headquarters.
The central London office in Derry Street, west London, was evacuated after violence broke out. One person was arrested and armed police remain at the scene.
The company confirmed that two members of the catering team had been involved in a “violent altercation”.
“We just heard screaming and running and people slamming doors,” said an employee, who did not want to be named.
The men were “running round chasing each other” and “slashing each other up”, he added.
Pictures posted to social media showed a stretcher at the scene.
A witness who works at Warner Music, which shares the building with Sony, said that as they were evacuated down the fire escape, she saw armed police running up to the fifth floor.
On the way out she saw a woman who works at Sony crying.
She told HuffPost UK: “Armed police stormed upstairs. We saw a girl from Sony and she was just crying and there were loads of crowds of people.
“It was a bit crazy. Obviously everyone was a bit scared. [When I saw the police with guns], I was shit scared.
“They has massive guns. They were running up the stairs and we were running down and that’s when we knew something serious had gone on.”
Northcliffe House opposite Sony HQ houses newspapers The Daily Mail, MailOnline, The Independent, Metro and The Evening Standard.
Trish Ellis, a personal assistant at the Mail on Sunday who witnessed the incident, said: “It started opposite our building in Derry Street, usual sirens and racket but then we heard shouting, and more and more sirens.
“A few people came out, then armed police were going in six-plus at a time, and more and more of them, but they seemed to be keeping people in the building.
“Gradually they started to release people in tens, twenties, [and] a stretcher turned up with all the medical kit on it, but just stayed outside.
“A [helicopter] appeared, still loads of armed police running up and down, and then thankfully over the time it ended up much quieter with 10 armed police standing outside, at ease.
″[An] empty stretcher went away and, thank God in heaven, all seems calm again,” she added.
A spokesman for the Met Police confirmed police had been called at around 11am on Friday. He said there was no evidence firearms had been involved in the incident, which is not being treated as terror related.
He added: “Officers, including firearms officers, and London Ambulance Service are in attendance.
“Evacuations are in place as precaution. At this time we believe two people have suffered injuries.
“Officer remain on scene and the incident remains ongoing.”
A London Ambulance Service spokesman said: “We were called at 11:01 today to Derry Street, W8, to reports of an incident.
“We sent an incident response officer, two single responders in cars and two ambulance crews to the scene.
“We treated two people at the scene. We took one to hospital and one to a major trauma centre.”