Homes evacuated when a 30ft (9m) hole appeared in back gardens eight months ago may have to be demolished, officials have said.
The hole appeared overnight and quickly filled with water
Nine residents in Greenmoor Road, Egremont, Cumbria, fled their 1960s-built bungalows in June 2005.
The area was used extensively for iron ore mining and the collapse is thought to have been caused by subsidence.
Home Group, which owns the houses, said further tests are being made which could lead to some being demolished.
Five people were allowed to return to their homes, but safety fears mean four others cannot.
The properties are owned by Home Housing, part of the Home Group, which appointed specialist consultant engineers to examine the site.
A spokesman for Home Group said: "We have told residents that further tests need to be carried out on the site.
"We have also told them that, regrettably, this may eventually mean that some properties need to be demolished on safety grounds."