Road workers in Bexley have discovered leaks following overnight works.
Contractors may have to keep barriers and temporary traffic lights in place for the next two days as they carry out emergency repairs.
A spokeswoman for Thames Water said: "We’re very sorry for the traffic disruption in Bexley.
"Our engineers are making essential repairs to a burst pipe and traffic lights are in place - unfortunately there was a fault with the lights this morning, which increased congestion in the area.
"The lights are now operating as they should and we’re working to fix the pipe and return the road to normal as soon as possible.”
A spokesman for Bexley Council added: "Thames Water works taking place in Bexley Village over-ran today (October 6) causing severe traffic delays to surrounding areas, particularly during rush hour.
"The works, to complete repairs to a leak in the carriageway of Bexley High Street, began at 7pm last night and were due to finish at 5am today.
"However, Thames Water encountered engineering difficulties which meant that the repair could not be completed in time.
"Temporary traffic lights are in place.
"The leak has now been repaired and we are expecting a temporary reinstatement to be in place by rush hour tonight and the temporary traffic lights removed.
"Thames Water will return at a later date to complete the permanent surface repair."
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As a result of the works, Highways England have said that drivers should expect long delays on A222 Bexley High Street at A223 Bourne Road, congestion on A223 North Cray Road to St James Way, on A223 Bourne Road to A207 (Crayford) and on A2018 Old Bexley Lane to A2 (Dartford Heath).
Highways England said: "Overnight works have been left in place after contractors found another leak, possibly for two days."
Highways England added that drivers should also expect long delays back onto the A2.
Bexley Council annouced the delays over Twitter.
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