The cause of the collapse is being investigated but it not believed to be connected to the recent bad weather and frozen pipes
Engineers are trying to find out why a 10ft (3m) wide crater appeared in a car park behind two blocks of flats.
Residents were evacuated after the road collapsed in Brynmair Close, Aberaman in Rhondda Cynon Taf, leaving a hole, believed to be about 12ft (3.65m) deep.
Nobody was injured and the area was fenced off while engineers worked to establish the cause of the collapse.
Rhondda Cynon Taf council said the hole had got bigger overnight and it needed to know why before repairing it.
Council officers are currently working on the assumption that the collapse is in relation to a culvert, but cannot be precise until the water has been drained from the bottom of the hole.
A spokesman for RCT Homes, which owns the flats but not the residential car park, said the crater had water at the bottom.
But he said he did not believe the collapse, which was reported on Tuesday, was connected to the recent bad weather and frozen pipes.
The hole in the car park got bigger overnight, the council said
The Coal Authority has already attended the incident and confirmed the collapse is not related to previous mining activity in the area.
Large machinery, including a pump and mechanical digger, have been brought in to help with the investigative work, while structural engineers are also at the scene.
Three flats nearest the hole were evacuated on Wednesday night - two residents are staying with their families and the third is in B&B accommodation.
Gerald Paget, who lives in one of the blocks of flats, said he was a "bit nervous" about the hole being so close to his home.
He said that since it was discovered the crater had been getting "bigger and bigger".
"Every half an hour you could hear all the earth falling away and crashing down," he added.
Nigel Wheeler, service director for street care at Rhondda Cynon Taf council which owns the car park, said: "We were made aware of the land collapse last night [Tuesday] and have been on scene ever since in order to determine what has caused the situation.
"Until we have established that, we are not in a position to make effective, safe repairs.
"The hole has already got bigger overnight, which is why it is so important we understand exactly what is causing the collapse in order to make it safe and allow residents to return to their homes."