A MAN has been arrested after a substance thought to be rat poison was sent in the post to a council worker, The Northern Echo has learnt.

The substance was sent in a letter to a member of staff at Durham County Council, together with a threatening note.

The intended recipient did not open the letter, but it was opened by another member of staff at County Hall, who raised the alarm.

It is understood the incident is in connection with their work activities, but no more details have been given.

In a statement Lorraine O’Donnell, assistant chief executive at Durham County Council, said: “This is part of ongoing criminal investigations and, as such, the council considers it is inappropriate to comment on the matter.”

An internal memo, circulated by health and safety officer Sue Kelly, had earlier warned that “although incidents of this nature and other acts of aggression are rare, there is a always a potential for such incidents, particularly in services where interaction with customers and the public occurs.

“The incident highlights the need for all employees who may handle or receive mail to be aware of the risk and to ensure that they are familiar with procedures in place within their service for handling mail and for reporting incidents should they occur,” it said.

Council managers have also been told to review the risk assessments in place within their services to ensure that “appropriate procedures are in place”.

A spokeswoman for Durham Police said: “We can confirm we are investigating an incident at County Hall, Durham, earlier this month.

“A man has been arrested and released on police bail pending further inquiries.”

The incident is the second in the space of a month in the region – albeit unrelated – involving a suspect substance being sent to offices.

Hundreds of people were evacuated after a mystery white powder was sent in an envelope to the Student Loans Company building at Lingfield Point, Darlington. A woman who opened it became ill and had to be treated by paramedics at the scene.