Two people have been injured in a five-car crash at the drop-off point for Heathrow Airport's terminal three.
A 40-year-old suffered neck injuries, while a 30-year-old was left with a head injury after the crash at 1550 BST.
A BAA spokeswoman said the drop-off point remained open and the airport was unaffected.
The police, fire brigade and ambulance service were at the scene. One eyewitness said it looked as if a high-speed collision had taken place.
He said: "Looks like a car travelling at speed involved in a collision in the drop off zone."
"Casualties [are] being stretchered away."
A Metropolitan Police spokesman said: "It was a five-car road accident in the terminal three forecourt.
"There have been no arrests at this stage."