Four fire engines and at least two ambulances were rushed to UCL after a fire erupted in the Roberts Building today.
The London Fire Brigade said about 25 firefighters attended the blaze after it received a call at 12:10pm.
It said a small part of a laboratory in the basement was destroyed in the fire.
The Brigade initially described it as a “small fire” on Twitter but witnesses say there was concern that the fire would spread due to the amount of flammable chemicals stored in the laboratory.
A mobile command centre was set up on Malet Street and at least two ambulances were on standby.
The Brigade said the fire was under control by 2:12pm.
No one was hurt in the incident but a cordon remained in place until around 3pm between Gower Street and Malet Street while the cause of the fire was being investigated.
A UCL spokesperson said the fire was related to a student experiment.
“The fire was quickly put out and there were no injuries. The building has now been ventilated and all but the two basement floors – which are being cleaned – have reopened.
“The neighbouring Malet Place Engineering Building was also evacuated temporarily as a precaution and has also reopened.”