Tests at Oxford's BMW car plant have failed to track down the source of a foul stench which householders say is becoming worse -- and spreading.

Brian Lester in his garden The smell, which was first detected in Blackbird Leys, is now being reported as far afield as Rose Hill and Headington.

Environmental health officers investigating the smell had thought bacteria in the car factory's water cleaning system might be to blame. BMW initially denied being responsible for the smell, but agreed to begin tests in the paint shop last month.

The test results have, however, ruled out the theory.

Residents have continued to complain to the city council about the smell, which first became noticeable at Christmas.

BMW workers have signed a petition demanding assurances from the company that it is harmless.

They described it as a foul, pungent chemical smell, which gives them sore throats, nausea and headaches and clings to their clothes.

Bill and Joan Summersbee, of Balfour Road, Blackbird Leys, are anxious that the problem is solved before the weather warms up so they can open their windows and use the garden.

Mrs Summersbee said: "We didn't smell it for a while, then it came back with a vengeance.

"I've also smelt it in Horspath, Cowley and Rose Hill. You can't open the windows or put the washing out."

Brian Lester, the chairman of Blackbird Leys Parish Council, sympathised with householders in the area who had suffered from the smell.

He said: "I'm very concerned that it has spread as far as Rose Hill and Headington.

"It makes you wonder whether if it affected north Oxford, they'd have the full force of the environmental health department out there looking for the cause."

BMW communications director Werner Rothfuss, said: "We have completed microbiological analysis and the concentration of bacteria is below the levels that could cause such a smell.

"We will continue a comprehensive cleaning programme over Easter, when we have a couple of days without production. We will have to see if this produces any change."