UPDATE 12:30 p.m.: Navy Regional Mid Atlantic security responded and completed through search of the sub and adjacent areas, officials tells WVEC.com. No explosive material found; nothing threatening found. The shipyard is now open and operating under normal conditions.
Law enforcement are investigating the incident.
PORTSMOUTH -- Navy personnel are also on duty because of a written bomb threat made against a ship inside Norfolk Naval Shipyard in Portsmouth.
Spokesman Jeff Cunningham told WVEC.com a threat about a bomb being placed aboard USS Maryland was found around 7:40 a.m.
"As precaution, personnel aboard Maryland and in vicinity of the drydock were evacuated. Navy Region Mid Atlantic security personnel have responded and are still inspecting the area," Cunningham said.
USS Maryland is in the yard for regularly scheduled maintenance.
He said work continues as scheduled on other parts of the yard.
Cunningham stressed this incident is not related to this morning's stabbing on Naval Medical Center Portsmouth, which is several miles from the yard.