Motorists are being urged to avoid Edge Lane in and out of Liverpool after it was closed in both directions after a carriageway collapse and concerns over the impact on a nearby gas main.
The road is shut between Beech Street and Laurel Road near the Devonshire Hotel – diversions are in force but major congestion and long delays are expected.
Highways engineers are in attendance with colleagues from the utilities to establish the cause of the collapse – which is six metres wide and three metres deep – and make it safe.
A council spokesman said: “We are working as fast as we can to establish the reason for the collapse and once that is done we will be organise repairs, but in the meantime we have had no choice but to close both sides of the carriageway for safety reasons.
“It is not possible at this stage to know when it will reopen but as soon as we can give a timescale we will.
“Our clear advice to motorists is to avoid the area until further notice.”