LOWER ALLOWAYS CREEK TOWNSHIP, N.J. (AP) — The Salem 2 nuclear plant in southern New Jersey has been taken offline after a leak of low-level radioactive water developed during routine testing of an emergency cooling system.

Plant operator PSEG Nuclear said the incident Thursday night posed no threat to plant workers or the public. But it’s not known when the plant will return to service.

Spokesman Joe Delmar said about 90 gallons of water leaked from a valve into the auxiliary building next to the reactor containment building. The water was collected through the floor drain system. It will be processed through the radioactive waste system at the plant.

The incident prompted officials to declare an “unusual event” the lowest level of alert—that lasted for about six hours.

(Copyright 2011 by The Associated Press. All Rights Reserved.)