The Mayor of Derry, Drew Thompson, today said he knew nothing about the trailer being stolen from outside a council-owned leisure centre in the Waterside until he was contacted by the North West Telegraph.

Police said the crime may have occurred up to three weeks ago - prompting fears that the material, some forms of which can cause lethal illness, may have already been dumped.

However the local council and a health body have moved to allay public concerns.

Fifty kilos of the material had been stored in the Ifor Williams trailer which was taken from the grounds of Lisnagelvin Leisure Centre.

A spokesperson for the Health and Safety Executive said that the risk to the public would depend upon the type of asbestos involved, and Derry City Council has confirmed that the material was bagged and airtight.

A spokesperson for Derry City Council said: "A registered asbestos contractor was employed by Council to assist in cutting access to effect repairs to the roof of Lisnagelvin Leisure Centre.

"The works were carried out as part of a planned procedure and at all times the required safety procedures were adhered to.

"A small amount of asbestos board was removed and securely bagged and stored in an airtight trailer for safe disposal by the registered contractor. Unfortunately the trailer was stolen and the police are currently investigating the theft."

When asked for comment, the mayor said angrily: "This is the first I've heard of it. I should have been told. There are a lot of questions to be answered here. Why is there a three-week gap?"

A spokesman for the HSENI said that more information about the materials was needed before they would issue any sort of warning.

"The risks associated with asbestos will depend upon the type and physical nature of the material involved and also how it has been contained."

He said that if the asbestos was in tile form and was sealed in plastic, risk to the public would be minimal.

The vehicle is white in colour and has a roller shutter door. Anyone with information can call 0845 600 8000 or 'Crimestoppers' on 0800 555 111.