Experts are dealing with a huge sinkhole in the back garden of a suburban property - the fifth reported in the UK this month.
Police were called to a building in Croxley Green, near Watford in Hertfordshire, at 6pm on Sunday after the 5ft-wide, 20ft deep chasm was reported.
Four homes - a house and three flats - were evacuated so the fire service and structural engineers could assess the situation in the village.
Speaking from the scene, Sky's Siobhan Robbins said: "One of the suggestions being looked at is the possibility that this might be an old well that's been exposed by the bad weather.
"The flats and a house were evacuated for a short time but they're all back in now."
A resident who lives nearby told Sky News: "A colleague of mine rents her property and she's had to have a huge hole about a metre square just to the right of her doorstep filled in recently.
"We joked that it was a sinkhole but they are popping up literally everywhere."
On Saturday, 17 homes were evacuated after a 35ft-wide hole opened up on the corner of a residential street eight miles away in Hemel Hempstead.
In both cases, the properties are in an area with high levels of soluble chalk in the ground - making it more vulnerable to sinkholes.
There are usually around 20 sinkholes a year in the UK, although many may appear in rural areas and go largely unnoticed.
But the latest incidents bring the number reported in urban areas to five in the last month alone.
In Kent, a huge void which suddenly appeared in the central reservation of the M2 caused days of chaos for motorists last week.
The 15ft-deep hole - which closed a 10-mile stretch of the motorway near Sittingbourne - was a dene hole, an underground structure made up of several small, chalk caves, the Highways Agency said.
In Barnehurst, southeast London, another huge sinkhole appeared in the back garden of a home a few feet from a child's trampoline.
Radiographer Gretel Davidson, was told she may have to pick up a £10,000 repair bill herself as the 17ft-deep chasm was on private property and too far from her home to be covered by her insurance.
On February 3, a family in High Wycombe, Buckinghamshire, spoke of their relief after they escaped injury when a 30ft-deep sinkhole opened in the drive of their home.
Teenager Zoe Smith's Volkswagen Lupo was filled with earth as it was swallowed up by the hole and her family were advised to leave home for their own safety.
Mother Liz Conran said "The car's on its side, it's full of soil and (our daughter) certainly ... wouldn't have got out of it had she been in it."
Experts are blaming the weather which has seen record levels of rainfall during December, January and February.
The rainwater turns acidic as it absorbs carbon dioxide in the air or combines with decaying plants, and dissolves rocks like chalk, limestone and gypsum.
Underground cavities become bigger, and as heavy rain makes surface layers of clay or gravel heavier, they can no longer be supported and collapse into the space below.
It is difficult to predict where sinkholes will appear but areas where activities like mining have created man-made holes tend to be more vulnerable.
Speaking about the Hemel Hempstead incident, Dr Helen Reeves, from the British Geological Survey, told Sky News: "We've had brickworks at this location - man-made activity, which has extracted clay to produce the bricks and certainly this is an important factor to consider why these events have happened."
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