Highways England are in the process of closing the M4 after a car overturned in a serious crash
The motorway is being shut between Junction 2 (Brentford) and Junction 3 (Heston).
Queues are reportedly building on approach to the scene of the incident, and delays are expected to increase for some time.
Highways England sent out the following tweet warning of the incident.
It reads: "We are in the process of closing M4 #GreaterLondon westbound between J2 (Brentford) and J3 (Heston) due to an overturned car. Met Police, London Fire Brigade and Highways England officers are on scene, delays building on the approach."
Other reports are describing the incident as a "serious accident" and warn drivers to try to find a diversion if at all possible.
We have spoken to Kerry Foster, a member of the public who treated a lady injured in the incident, who said: "There was an overturned Land Rover and two passengers, one male and one female.
"Both of them had suffered facial injuries, and emergency services are still on the scene."
We will be bringing you live updates as they become available:
The road has re-opened
M4 between M4 Junction 2 and M4 Junction 4 (M4 Heathrow Spur) - The M4 westbound has reopened following an earlier incident. Drivers are advised to seek alternative route. Traffic westbound is being di #LondonTraffic https://t.co/hDbK2yTa6I pic.twitter.com/4TeoeXUQQT— Jambuster (@JambusterLondon) 16 September 2018
Everyone rallied to help
According to Kerry Foster, several people rallied to help the injured couple.
She said: “Everyone who helped were so calm and kind. I had some water that I brought with me from my car, another man brought a blanket for the lady and I believe someone else brought something to cover the man.”
"We could still smell fuel leaking"
Witness Kerry Foster who helped the injured couple in the overturned car said: “The smoke subsided before the emergency services arrived, but we could still smell fuel leaking.
“I asked someone to turn off the ignition and remove the keys, hoping that the vehicle wouldn’t ignite as we were still quite close to it and it would have meant having to move the couple again, further away.”
"Long and very deep cut"
Kerry Foster said that a woman injured in the collision had a long and very deep cut on her face. She added the woman seemed confused and was concerned for her partner.
"We could see the overturned vehicle on the grass"
Kerry Foster, who helped the two injured people at the scene, said: “My daughter and I noticed a huge plume of dust ahead as we were driving towards Slough. It seems the dust was where the vehicle had come off the M4 and along the ditch to the left of the hard shoulder. As we approached, we could see the overturned vehicle on the grass and smoke was coming from the front of it.”
M4 between Junction 2 and Junction 4 (M4 Heathrow Spur): There is a full westbound carriageway closure due to a collision. Expect delays.— TfL Traffic News (@TfLTrafficNews) 16 September 2018
What we know so far
The M4 has been closed between Junction 2 and 3 after a car overturned shortly after 1pm on Sunday, September 16.
A witness at the scene has said the overturned car is a Landrover, and that two people have sustained facial injuries.
Long queues are building and delays are increasing.