In a statement faxed to the Knutsford Guardian Manchester City Council said the methane and toxic carbon dioxide had been found near an old tip.

"Tenants should not be alarmed by this development," said City Clr Basil Curley.

"The city council has surveyed the homes which we have been advised as being at risk and we have found no traces of methane."

The council has taken advice on how to deal with the problem and plans to set up a free advice line for worried residents.

Special meetings have been organised so they can question experts and more houses could be checked before the survey is finished.

"We are taking all the steps necessary to deal with the problem," he said.

More than 30 bore holes were dug around Longridge and Shaw Heath and higher than normal levels of gas were found at eight sites.

Investigations will take more than two months. But the discovery has delayed the transfer of more than 450 homes from the council to new landlords Manchester Methodists.

"It is like when you are taking a mortgage out and the lenders only lend money if they are sure everything is all right," said spokesman Ian Hamill.

"Before they agree they have to be happy that there won't be a problem for the next 30 years and beyond."

Government officials have given a November deadline to complete the transfer, but Mr Hamill refused to say when it could happen.

The Methodists had planned to freeze tenants' rents, but because of the delay their bills will rise in April.

"They will stay as Manchester tenants and the status quo will remain until they become tenants of the social landlord," said a council spokesman.

Residents have been asked to continue to report repairs and call the council with any other questions on 0161 953 2525.

They are invited to two meetings at St John's Wood School at 7pm on March 20 and 22 to discuss the delays.

There will also be two drop-in sessions at 106 Longridge on March 21 from 10am-12pm and 2pm-4pm.