Hospital staff have been injured and dozens more people were evacuated after an “accidental chemical spill".

Emergency services attended Hemel Hempstead Hospital at around 10.16am today over reports of a leak in the Verulam Wing.

The wing, which makes up around half of the hospital, had to be evacuated as photos showed people waiting outside the building.

People waiting outside if Hemel Hempstead Hospital. People waiting outside if Hemel Hempstead Hospital. (Image: Supplied) A spokesperson for the West Herts Teaching Hospitals Trust said: “Three staff members have received treatment for minor injuries following the incident, which relates to an accidental chemical spill."

They said the incident was “contained” and would not affect local residents, while the Urgent Treatment Centre, blood clinic and radiology departments remained open. 

The source of the leak has now been confirmed to be cleaning fluid from a decontamination machine, and the injured staff have now been discharged.

“Please attend your outpatients appointment as normal and follow the advice of staff on arrival. We will contact you if your appointment is cancelled,” they added. “We will be in touch with further updates, as necessary.”

Hospital services are set to reopen in phases this afternoon while endoscopy will remain closed until further notice.

An eyewitness said she arrived for an appointment at around 11.25am to find that the entrances had been blocked and around 50 people were waiting outside.

Hertfordshire Police are assisting with road closures around the building.Hertfordshire Police are assisting with road closures around the building. (Image: Supplied)

Hertfordshire Fire and Rescue Service, East of England Ambulance Service and police all attended the scene with officers enforcing road closures around the building.

Firefighters in gas-tight suits and breathing masks also worked to try to identify the chemical and to clear up and ventilate the affected area.

A spokesperson for the hospital trust confirmed the emergency services left the scene by around 2.30pm, adding: “Thank you to staff, police, ambulance, and fire and rescue colleagues for their prompt and efficient response.”