Six hospital staff have been treated in A&E after an “unconfirmed substance” was spilled in an on-site laboratory.
The spillage at Addenbrooke’s Hospital in Cambridge was reported at 11.20am on Monday, the trust said.
More than 20 firefighters attended and six members of hospital staff were treated for respiratory issues.
The hospital said the staff are “now medically well and continue to be monitored”, adding that there has been “no significant impact on patient services”.
The laboratory was evacuated as a precaution, it said.