A bomb disposal unit is responding amid an “ongoing incident” on Wrexham Industrial Estate.
The Wockhardt vaccine factory is understood to be closed off.
The plant is responsible for the “fill finish” of the life-saving jab and has a range of production lines at the industrial estate.
North Wales Police and the Royal Logistic Corps are in attendance.
A police cordon has been put in place in surrounding areas and the public has been urged to stay away.
Ash Road has also been closed in both directions between Bryn Lane and Abbey Road.
A North Wales Police spokesman said: “We are currently dealing with an ongoing incident on the Wrexham Industrial Estate.
“The roads are currently closed and we would ask the public to avoid the area until further notice.”
This is a breaking story…more to follow