Thousands of litres of foamed concrete are being pumped into a massive sinkhole in St Albans.

The 66ft (20m) wide and 33ft (10m) deep crater opened up across gardens and driveways in Fontmell Close last week.

Work to fill the hole is expected to continue into Thursday.

Hertfordshire County Council said once the hole is filled to within a metre from the top, more surveys will be carried out and utilities will be permanently reconnected.

The hole first appeared a week ago and injured a postman working on the street, Royal Mail said.

Royal Mail said the hazard first appeared on September 23 when a postman injured himself on a drain cover which gave way.

Hertfordshire County Council inspected the footpath but concluded there was "no reason to suspect that the hole would collapse".

Royal Mail spokeswoman Sally Hopkins said: "Royal Mail can confirm that one of our postmen was delivering in Fontmell Close last week (Wednesday September 23) when a drain cover gave way.

"We're happy to say that the postman was not seriously injured and we reported this incident to the council."

Most homes in the area have had temporary fixes on their water and electric supplies, but gas and telephone lines are gradually being reconnected.

A private security firm has been watching properties in Fontmell Close and Bridle Close 24-hours-a-day since Friday evening, with a number of residents unable to return to their homes.

Jenny Burley, of Seymour Road, praised the council and emergency services handling of the sinkhole aftermath.

She said: “I’ve been incredibly impressed with how the whole thing has come together, especially something as big as this. I think it’s been handled as well as it could have been.

"People I know who live down here that I’ve spoken to say everyone has been very considerate and they have told them what’s happening and kept them in the picture.”

Other residents whose homes back onto Fontmell Close said apart from a disruption to the water and electric supply in the early hours of Thursday morning, they were unaffected by the sinkhole and were carrying on as normal.

Tan Ahmed, who lives in Seymour Road at the entrance to Fontmell Close, said he was woken by the flashing lights of the fire engines moments after the road collapsed.

He said: “We didn’t here anything, we were woken up by the flashing lights of the fire engines and police cars. The emergency services were very good, they did what they could.”

He continued: “We’ve managed to keep all our utilities. I am concerned about the house insurance going up, I will argue that it should not because we are not on that site but it is a concern.”

A geophysical survey has begun under the housing estate, which local historians say was once covered in brickmakers' clay pits, to try and identify any further areas where sinkholes could occur.