By Malcolm Prior
BBC News Online, Reading
For the Berkshire town of Reading, bricks were once a major source of its economic and physical growth.
There was a major ground collapse in January 2000
But that industrial heritage could now turn out to be the downfall of many.
Hundreds of residents are living in fear of their homes collapsing into one of the many forgotten chalk mines on which the town is built.
More than 30 homes had to be evacuated after a major cave-in in Field Road in 2000 and millions of pounds are now to be ploughed into making the area safe.
About 700 residents in 285 houses in the Coley area are being asked to sign up for drilling tests aimed to one day end the risk of collapse once and for all.
Eighty of those attended a public meeting on Tuesday night to hear the latest on the threat posed to their homes.
The investigations will cover a 2km area across Coley
Geotechnical specialists and council bosses outlined their plans to carry out nine months of investigations at a cost of £2.56m across a 2km area.
To know the true extent of any possible danger, they need to identify how many of the caverns have already collapsed and filled in, how many have partially collapsed and how many are still completely empty.
It is these voids that pose the biggest threat.
Dr Clive Edmonds, of contractors Peter Brett Associates, which is undertaking the work, told BBC News Online: "It is not a high risk necessarily. It is perhaps a moderate risk at this stage.
"While we recognise that there's always the possibility that empty voids could still be found in the ground and there might be a possible threat of collapse, there's no such evidence at the moment to suggest such voids."
Maps, records and geological surveys have already been closely examined to find out where the mines are and how far they stretch.
Reading itself is built on a mixture of clay and chalk.
As brickmaking became popular in the late 18th and 19th Centuries, chalk mines also were dug.
Such mines were often worked alongside brickworks on the outskirts of the town, providing chalk to mix into the bricks.
Engineers intend to probe the roads in the area
When the mines eventually closed down, thousands of new homes were soon built on top as the fledgling town pushed past its original boundaries.
Coley is not the only area affected, with a series of holes appearing in Palmer Park on the other side of town in 2001 and a network of mines known to be under Emmer Green.
Why Victorian planners thought it wise to build on mine cavities is a puzzle that still troubles Dr Edmonds.
"There was mining in Field Road during the 1770s to the 1830s and the houses affected in 2000 were built in 1881.
"It looks like we have houses built on chalk mines 50 years after they were abandoned.
"It's strange that they were not aware of it. One can only assume that it was a commonplace activity and no more mining had taken place.
"Lifespan was also shorter so perhaps 50 years was beyond most people's lifetimes," he said.
But now the mines are known about, Reading Borough Council is keen to take action.
Homes in Field Road were made safe after a number of collapses
When the new phase of investigations begins in September, engineers will probe the ground to find any voids, taking samples and using remote-controlled cameras underground.
The council needs homeowners' permission to carry out the tests and they have been given until the end of July to do so.
Despite concerns about the survey's results affecting the value of their homes, the council is urging residents not to ignore the problem.
In a statement the council said it was "impossible to say for sure" how property prices would be affected by the findings.
But it added: "So far the property market in Coley has generally held up very well despite the uncertainty that has been around ever since the collapse in Field Road.
"The homes in Field Road are now some of the most stable and secure in Reading.
"At the end of the investigations people will know exactly where they stand."
And Dr Edmonds warned: "The main thing to consider is if we do not do the survey another Field Road collapse could occur."