One of the main roads into Lowestoft town centre will be closed for up to three weeks while emergency repairs are carried out.
London Road South will be closed from Mill Road to the A12 while repairs are carried out to the sewer underneath the road.
One lane of the road has been closed since the end of August after a problem with the sewer was reported.
And investigations this week have revealed a manhole which has dropped into the sewer has meant the road needs to be fully closed to enable the repair.
The closure will mean drivers will only be able to access Marine Parade, the main road which runs along the seafront, when travelling in a southbound direction across the Bascule Bridge.
Simon Love, head of collection services for Anglian Water, said: 'This is an emergency road closure - as soon as we were able to assess the full extent of the problem we shut both lanes to ensure public safety.
'It's a complicated job but we are working as many hours as possible – from dawn to dusk and throughout the weekend – to get this job done and the road opened as quick as we can.
'We aim to keep people in the area informed as much as possible – we will be sending letters to local residents and businesses, we will be updating our In Your Area webpage, posting on social media and we'll have digital signs up giving live updates.
'We would like to apologise to anyone inconvenienced by this work, but please be rest assured we are working as hard as we can to get this fixed and traffic moving again.'
•How will this road closure affect you? Email lowestoft.journal@archant.co.uk
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