A mine shaft has collapsed leaving a 75ft-wide crater in back gardens forcing families to flee their homes.
Eight houses had to be evacuated after the hole opened up while a drilling rig was being used to cap the former iron ore mine with concrete.
A worker had to be rescued as he was harnessed to the machine and became trapped in the shaft.
Police were called out to Egremont in West Cumbria at 1.30pm yesterday after reports of the collapse.
It is believed the drilling rig fell around 50ft into the shaft which caused a huge hole to open up about 75ft wide.
The site was being monitored after reports of some land slippage over the past few months.
Inspector Phil Davidson, of Cumbria police, said the houses had been evacuated by Copeland council for health and safety reasons.
The area has been been cordoned off and security provided by a private contractor.
Drivers have been urged by police to avoid the area. There are no reports of anyone being hurt.
Ryan Rickerby saved the worker who was trapped in the 80ft-deep hole after the machinery he was in plunged into the ground.
He witnessed the incident from his kitchen window, as the area being worked on lies at the bottom of his garden on Howbank Road in the town.
Mr Rickerby , 25, said: 'I was washing up in the kitchen and my window looks right on to my garden, and the garden is happening behind. All of a sudden, the garden literally just fell into the ground.
'There was a huge cloud of dust and a loud rumble and when I could see what happened, I realised the floor had literally just fallen through.
'There were lots of workmen around at the time, and I heard one of them shouting, so I went outside to see what was going on.
'The drilling rig they had been using had fallen into the mine shaft. It wasn’t on at the time.
'A worker was harnessed to the machine and he was stuck in the mine shaft.
'I managed to climb down and unclip him and pull him out.
'It’s really scary thinking back on what happened. It’s a miracle no-one was hurt.'
Mr Rickerby, a pipe fitter at Sellafield Nuclear Plant in Cumbria, is not able to get back into his house after he and his father were evacuated yesterday afternoon when the ground collapsed.
Linda Clarke, 58, who also lives on Howbank Road, said: 'There’s a lot of speculation as to why the ground collapsed - people are saying it’s due to the amount of rain we have had, leaving the ground really soft, but we’re not sure.
'I hear the garden just gave way, it’s scary to think that can just happen right in front of your eyes.'
A spokesperson for Copeland Borough Council, who own the land, said: 'We have been working intensively for some months to monitor movement related to an historic mineshaft in Egremont and yesterday we began work to fill and cap the shaft.
'During the works yesterday there was a slump in the land around the top of the shaft. Thankfully nobody was injured but some equipment fell into the hole. We ceased work and closed off the area for safety reasons.
'Eight households have been evacuated as a precaution whilst the immediate investigation continues.'
In August this year residents of Egremont faced further misery after the entire side of a house fell into the flooded River Ehen.