Emergency crews were alerted shortly before 8.30am to an incident at Leicester Royal Infirmary. Leicestershire Fire and Rescue Service scrambled to an Accident and Emergency (A&E) unit amid fears of an electrical fire.
Crews investigating the incident reported the smell of smoke following a blown fuse in a pathology lab.
Fire crews have secured the location and have now been stood down.
There are no reports of any injuries.
A fire call handler told Leicestershire Live: "We were called to investigate a smell of smoke.
“There was a blown fuse in a pathology lab so there's nothing major happening.
"We did some ventilation and are now standing down."
Ambulances to the city centre hospital had earlier been temporarily diverted away.
Earlier this week, a new study suggested patients in Leicester face the longest waiting times in the country.
Leicester General Hospital has an average waiting period of 75.9 weeks or 17.5 months, according analysis of the nine most common procedures by the law firm Bond Turner.
Leicester Royal Infirmary had the second longest wait time at 75.4 weeks– above the nationwide average of 52.6 weeks.
The study collected NHS data from 52 of the biggest hospitals around the UK from September 22-28.
This is a developing news story, more to follow.