A waste company has said its landfill site has been given "a clean bill of health" after "horrendous" smells were reported in the Redhill area of Surrey.
Reigate and Banstead council said about 18 complaints had been received about a smell "similar to gas or having a sulphur-like quality".
Environmental health teams thought the source was a Biffa landfill site - but Biffa said it was inspected last week.
The firm has asked people to report any smells so it can investigate them.
Biffa Waste Services spokesman Barry Walton said: "Nothing has changed on the site [in Cormongers Lane].
"But there are a number of [other] operations nearby which could give rise to smells."
He said a gas works had been dismantled recently and there was a sewerage farm nearby.
"We are routinely inspected by the Environment Agency," Mr Walton said.
"They visited last week and gave us a clean bill of health.
"If anybody does smell an odour in the area, the best thing they can do is contact us," Mr Walton added.
He said £100,000 had been invested in the site since Christmas which was aimed purely at making sure there was no odour.
A statement from Reigate and Banstead Borough Council's environmental health team said: "The site takes gas control seriously and a number of measures are in place to prevent and minimise gas emissions, including odours."
The council added that it would be down to the Environment Agency to take any necessary action as that was the body which operated the landfill site's permit.
Thames Water operates two sewage treatment works in the area, one at Earlswood and one at South Merstham.
But it said it had not been approached by the Environment Agency over the Redhill smells and had "received very few complaints about odours in the area".