The Asda superstore at Brighton Marina is likely to stay shut until the end of next week because of the risk of more cliff falls.
Geologists have been called in to examine the chalk cliffs at Black Rock, directly behind the store, to find out whether there could be a repeat landslip.
The store has been shut since Monday, when hundreds of tons of chalk tumbled across the Undercliff Walk and into the yard behind the store.
Almost 100 shoppers and staff were evacuated after the rock fall, which blacked out electricity at the store and destroyed the water tank used to supply the sprinkler system.
A series of holes and cracks have appeared at the top of the cliffs since last week's rock fall.
Geologist John Cooper, of the Booth Museum, Brighton, said the cracks suggested more falls could be imminent.
Asda's regional marketing manager Jason Sharpe said the store would not reopen until geologists said it was safe.
He said: "Our prime concern is the safety of our customers and colleagues and obviously we have to wait for the report to make a decision."
"We can't say when it will be open but certainly not for the next seven days.
"Certainly not before Wednesday or Thursday but I would say Friday is probably the day we would open."
The petrol station, away from the area at risk of repeat rock falls, is still open and Asda is running a free bus service every 15 minutes from the Marina to its Hollingbury branch.
Brighton and Hove City Council earmarked £500,000 for work to stabilise the cliffs at Black Rock before last week's rock fall.
The Undercliff Walk has been closed since another huge rock fall on the same stretch of cliffs in December.
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