The Navy says the blast happened at Weapons Station Earle in Middletown at around 9 a.m. Tuesday.
The Navy says the explosion was confined to the boathouse where the routine maintenance was being done.
One sailor has been hospitalized with serious injuries. Seven other sailors and civilian employees sustained minor injuries, mostly smoke inhalation.
The Navy is withholding their names until relatives can be notified.
The Navy says no ammunition was involved in the explosion.
The cause is under investigation.
Naval Weapons Station Earle provides ammunition and explosives for vessels.