Residents in part of Cardiff are being warned to take special precautions after traces of arsenic and other chemicals were found in the soil.
The area around Cardiff City's Ninian Park ground is affected
Cardiff Council advised people to thoroughly wash and peel any fruit and vegetables grown in Leckwith.
A structural survey of council homes in the area has also indicated some possible underground movement and a full survey will be carried out.
Allotment owners were warned about the dangers earlier this month.
Vegetables grown at Leckwith allotments were found to contain enough lead and arsenic to be harmful in the long term.
A council official said investigations had revealed "unacceptable levels of contamination".
Children and pregnant women especially were advised to limit the amount of Leckwith-grown produce they ate.
The council found 'unacceptable levels of contamination'
Now the authority has extended its warning to include roads near the allotments and near Cardiff City Football Club.
It said the results of independent tests on 12 soil samples carried out in the area in June show "some exceed soil guideline values for arsenic, lead, nickel and mercury".
Residents were told they should make sure they washed their hands after working or playing in the gardens.
Footwear which could transport soil into homes should also be scraped and cleaned.
The council said it was issuing "standard hygiene advice".
Richard Spear, a milkman living in one of the affected streets, Dunraven Road, said the news was a bit worrying.
"They're doing surveys of the area, checking different things and taking samples of the soil.
"If there is nothing to be alarmed about why are they doing all these surveys?" he asked.
He said the area had been a railway yard and later a landfill site, and lots of material had been buried on the site.
Richard Spear: News is 'worrying' for residents
Mr Spear said the council was holding information sessions in Leckwith Stadium over the issue.
"I'll be going along to listen to what they have to say.
"I want to know why they have just found it now," he added.
Other roads affected include St Donats Road, Newton Road and the properties fronting onto Sloper Road between Ninian Park and Newton Road.
The area also includes the east of Sloper Road, north of the Cardiff Bus depot, south of Cardiff City FC and up to a former rail track.
The council said the city's industrial past was likely to be responsible for the ground conditions. The properties were built in the 1930s when less was understood about the nature of the conditions, and building control was less stringent than today.
A detailed consultant's report into the environmental sampling and structural surveys is due to start in the New Year with the reports expected to be completed by July 2005.
In a statement the council said "a number of issues that require further assessment in relation to the structural integrity of the buildings caused by some underground movement resulting in settlement of some external walls"