Three people were spotted on the roof of the 28-storey CIS tower in Manchester city centre.
Eyewitness Joe O'Donnell spotted the group standing on top of the iconic Miller Street skyscraper at around 8.30pm last night.
He told the Manchester Evening News that they looked like males, and didn't appear to be wearing any safety equipment.
"They were just walking around on top of it", he said.
"They were on there for about 20 or 30 minutes."
He said it appeared that security guards then told the group to safely come down from the roof.
The 387ft, 28-floor tower was once the tallest building in Europe when it was completed in 1962.
It was occupied by the Co-operative, before being sold to Castlebrooke Investments for £66m in May 2017.
The tower will undergo a £150m revamp after city planners approved plans to provide new 'high quality' offices, retail and leisure facilities.
