At least one flight was evacuated following the incident, thought to be a collision between two ground vehicles.
Heathrow Airport’s official twitter account said: “Following an incident on the airfield involving two members of staff, an investigation is underway and we are working with the Police.
“This incident didn’t involve any passengers and is not expected to cause any impact on journeys today.”
However they later said a plane had to be evacuated.
A spokeswoman said: “We are dealing with a serious accident involving two vehicles on the airfield.
“We are working closely with the emergency services and updates will follow.
“The airfield remains open and we will work to minimise disruption to our passengers’ journeys.”
This is a breaking story, more to follow…