Parts of the University of Manchester have been evacuated over concerns a chemical in the science department has become explosive.
Police were called to the University of Manchester Institute of Science and Industry building following report about a potentially explosive chemical.
It is reported some acetone peroxide had "crystallised" and become hazardous.
The surrounding area has been cordoned off and police are advising people to stay away while the situation is ongoing.
Acetone peroxide is a highly explosive chemical which has been known to be used by terrorists for homemade devices.
However, police stressed that the incident does not appear to be terrorist related.
The bomb squad are said to be assisting with the emergency services while the cordon is in place.
A Greater Manchester Police spokesperson said: "Police are evacuating a building on Sackville Street after an explosive chemical was found at a University of Manchester Institute of Science and Industry building.
"At around 11.30am on Wednesday 4 March 2015 police were called to the Paper Science Building, 79 Sackville Street in the city centre after reports that some acetone peroxide had 'crystallised' making it potentially explosive.
"As a precaution, officers have evacuated the buildings in the immediate vicinity.
"Road closures are in place on Sackville Street, Whitworth Street, the slip road to the Mancunian Way and Princess Street.
"Motorists and pedestrians are advised to avoid the area."
A Greater Manchester Fire and Rescue Service spokesperson added: "There is an evacuation of the building and surrounding buildings as well as road closures. We have a 150m cordon in place and the army bomb disposal squad have been called to assist us.
"I would stress that the situation is stable at the moment. However, it would be helpful if people and traffic would avoid the area."