Dartford Crossing sign problems cause tunnel disruption
Problems with a gantry sign shut part of the Dartford Crossing between Kent and Essex, causing disruption.
Two lanes of the M25 at the Dartford tunnel were closed, leading to queuing traffic between junctions 1a and 31 because of the faulty sign.
The Highways Agency said the lanes reopened by 09.00 GMT but warned motorists to expect delays.
The closure comes less than a week after the new Dart Charge was introduced to ease congestion.
The new cashless payment system came into force at 06:00 on Sunday, replacing the toll booths on the Kent side of the crossing.
Work on a new road layout at the crossing is expected to be completed by Spring 2015.
On average more than 140,000 vehicles use the River Thames crossing every day.