Engineers at Suffolk Highways are working to fix a "constant flow of water" which has left a major road flooded since New Year's Eve.
The A143 Compiegne Way in Bury St Edmunds has been closed since Sunday, December 31 after heavy rainfall left it submerged.
The prolonged closure has caused heavy congestion in and around the town centre as drivers have been forced to find alternative routes.
A spokesman for Suffolk Highways said: “There is still a constant flow of water which we are investigating, including the use of a CCTV in the drainage today.
"We’re cleaning the pump today to see if it needs to be repaired or replaced.
"Also today, we’re carrying out some repairs to about 30 metres of verge and have road sweepers on site continuing to remove detritus.
"We have planned repairs to road defects and potholes starting from tomorrow.
"We also have our streetlighting team on site today making the most of the closure by replacing a streetlight column.
"Thank you again for your patience, we apologise for the ongoing inconvenience this is causing. These works remain our top priority."
Speaking previously, Cliff Waterman, councillor for the Eastgate ward which covers Compiegne Way, said: "It is frankly shocking that an important road in and out of Bury St Edmunds has been allowed to flood to begin with, and clearly there are not adequate drainage provisions there.
"For residents of my ward it is appalling because they have non-stop traffic queues outside their houses and people cannot move in and out of the side roads easily.
"It is down to a lack of proper planning and a lack of proper investment in our roads."
Vandalism to control gear delayed clear-up works in the west Suffolk town but teams from the authority were able to clear 72,000 gallons of water from the road on Wednesday last week.
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