A 15ft-deep sinkhole has closed the M2 - and experts claim the wet weather could be to blame.
Dozens of engineers are investigating the hole near Sittingbourne in Kent but the Highways Agency is refusing to state when the motorway could reopen.
It is unlikely to be in time for this morning's rush hour.
"We're not putting a timescale on it at the moment," Highways Agency spokesperson Kelly Barnes told Sky News.
"We're investigating the cause and then it's a case of seeing how we repair it.
"One of the main reasons we closed the motorway, which we never do lightly, is for safety reasons.
"People should anticipate that it will remain closed overnight and into rush hour on Wednesday."
One potential solution could be to pour foam concrete into the hole - but more extensive structural work could be required.
Engineers are being aided by fire crews who have provided camera equipment enabling them to scan the hole.
Long tailbacks developed either side of the 10-mile stretch following the closure ahead of Tuesday afternoon's rush hour.
Drivers travelling to and from Dover are advised to use the M20.
A representative from the AA believes the hole, which is almost 17x7ft across, could have been caused by the extreme weather being endured by much of southern England.
"The M2 started operating in 1965 and I am not aware of any previous collapses so perhaps this is yet another casualty of the exceptionally wet weather," said AA roads policy head Paul Watters.
"We hope the Highways Agency can quickly resolve the problem as this is a key route to the port of Dover and to east Kent."
Professor Amir Allani, professor of civil engineering at Greenwich University, agrees with the AA.
He said: "It may be due to the current rain and flooding underground has created the erosion which, in time, has facilitated the layers above the weak strata to collapse."
A signed diversion is now in place via the A249, the M20, the A20, the A252 and the A251.
Motoring organisations have campaigned for more funding to fix and prevent holes on the road network, but the AA claims no amount of money would have prevented Tuesday's incident.
"Thankfully this was on the central reservation," said company president Edmund King.
"If a hole of this nature had opened up on a carriageway it could well have led to tragedy.
"I don't think this is anything to do with potholes or general maintenance.
"There seems to have been some structural anomaly - perhaps some sort of geological fault or an old mineshaft.
"Clearly, it's a concern that this has happened on a busy motorway that leads to and from the coast.
"Engineers will want to deal with this as soon as possible.
"If the stretch of motorway stays shut it will cause traffic problems, but safety must come first."
Earlier this month, a sinkhole measuring 30ft-deep swallowed a car after opening on the driveway of a house in High Wycombe.
Nobody was inside the VW Lupo when the ground on Main Road in Walter's Ash gave way.
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