A large quantity of solvent which got into the city's sewerage system knocked out the odour control process at a water treatment works at Salt End.

The smell, which is now slowly going, has led to a number of complaints, Yorkshire Water said.

The company has launched an investigation into how the solvent came to be in city's sewers

Crippling effect

Simon Hodgson from Yorkshire Water said their inquires had so far drawn a blank.

"We don't know if this spillage was accidental or deliberate but it has had a crippling effect on the treatment process at our works in Salt End," he explained.

"This has led to a very strong smell which isn't a risk to health but is extremely unpleasant for people living an working nearby."

Mr Hodgson added that everything possible was being done to mask the smell and things were beginning to return to normal.