AN OFFICE building was evacuated today when a council worker reported an allergic reaction after opening an envelope.

Police sealed off the premises near Stanley, in County Durham while the source of the possible reaction was traced.

Investigations are ongoing, but police are not linking the incident to two recent cases in Darlington and Durham City when white powder was sent through the post.

Speaking at 6.45pm tonight, a spokeswoman for Durham Police said: "A full examination of the premises has failed to find any noxious or harmful substance and the incident has been stood down."

Staff were evacuated from Comeleon House, on Tanfield Lea Industrial Estate, this afternoon and police and other emergency services were called to the scene.

Speaking earlier, the police spokeswoman said: "A member of staff who opened an envelope reported a possible allergic reaction.

"The premises have been sealed off as a precaution to enable the source of the possible reaction to be established".

The 3,000 square metre building houses a number of Durham County Council workers, including some of the authority’s IT staff and also the design and print section.

A spokesperson for Durham County Council said: "Following an incident in which a member of staff reported a possible allergic reaction after opening some post an investigation has been launched.

"This enquiry will involve both internal and external agencies, including the police and fire service.

"The council is not able to comment further."

Last month, a man was arrested after a substance thought to be rat poison was sent through the post to County Hall, in Durham.

In an unrelated incident last month, hundreds of people were evacuated from the Student Loans Company building, at Lingfield Point, Darlington after an envelope containing a mysterious white powder was opened by a woman office worker.