Sasebo Naval Base in Japan is home to a number of U.S. Navy vessels, including the USS America amphibious assault ship. (Jonathan Snyder/Stars and Stripes)

Two Japanese contractors were declared dead Tuesday after they were pulled from a tank on a barge at a Navy base in southwestern Japan, a Sasebo Police spokesman said Wednesday.

The men were found unconscious aboard the commercial barge used to service a U.S. vessel, Sasebo Naval Base spokesman Aki Nichols told Stars and Stripes by email Wednesday.

The men — Takahiro Sasahara, 54, and Seitaro Hamada, 33 — were confirmed dead at off-base hospitals, the police spokesman said by phone Wednesday. They were working on a sewage treatment system for the vessel.

The base called the Sasebo city fire department at 12:07 p.m. to report two men found in a 16-foot-deep tank and an odor of gas at the site, a spokesman for the city’s fire bureau said by phone Wednesday.

Some Japanese government spokespeople may speak to the media only on condition of anonymity.

The men, in cardiac arrest, were lifted from the tank by base firefighters after the local firemen arrived, the bureau spokesman said.

“The base is assisting and cooperating fully with the Nagasaki Prefectural Police who have initiated an investigation into the incident,” Nichols said.