An explosion at a Navy base in New Jersey on Tuesday left at least eight people hurt, one of them seriously, the authorities said.

The Navy said the blast occurred around 9 a.m. in a marine boat repair shop at the Naval Weapons Station Earle, in Monmouth County. Workers were doing routine maintenance at the time of the explosion.

Naval officials said that the cause was still under investigation and that the damage was contained in the boathouse area.

Seven of those injured were treated at area hospitals - most for smoke inhalation - and had been released by Tuesday afternoon, the Navy said. One person, who suffered a broken arm and underwent surgery, remained hospitalized.

The base covers more than 12,000 acres and has a work force of 1,500 people. It plays a vital role in supplying weapons for Navy ships, including all ordnance for the Atlantic Fleet Carrier and Expeditionary Strike Groups.

Ammunition and ordnance operations were not interrupted because of the explosion, the Navy said.

The base's main complex is 15 miles west of the central Jersey Shore. There is also a waterfront center in the Leonardo section of Middletown Township, where the explosion took place.

The base features one of the longest pier structures in the world, stretching two and a half miles into Raritan Bay, which allows ships to be resupplied far from shore.