All lanes have now re-opened on the Dartford crossing approach, after a diesel spillage brought traffic to a standstill.
Highways England are still warning drivers to expect to add on at least two hours to usual journey times.
A diesel spillage across three lanes of the M25 has led to 20 mile queues on the approach to the Dartford crossing.
The incident, which took place at junction 31 in Essex shortly after 12.30pm, has caused major disruption throughout the afternoon, creating additional congestion on the A2.
A transporter broke down, spilling fuel across the road.
An Essex Roads Policing Unit spokesman said: "Looks like this will be a long one as they need to resurface.
"I appreciate on a Friday afternoon this is a real pain, but unavoidable - please remain patient."
"Cameras are on and recording.
"Anyone using the hard shoulder or driving recklessly will be dealt with."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here