CHANGWON (Yonhap News) ― A moored Navy guided missile patrol boat under construction sank at a shipyard due to strong winds, the shipbuilder said Monday.

Sources said the 430-ton Gumdoksuri Class patrol killer guided missile boat started sinking at around 3 a.m. as it was pounded by strong winds and waves. The boat, armed with 76 millimeter guns, was one of 24 being built to replace smaller Chamsuri Class patrol boats serving in the Navy.

The name of the shipyard on the southern coast was not revealed, although the builder confirmed that roughly 60 percent of the work, including the engines, was on board at the time of the accident.

“It started sinking by the stern, resulting in roughly four-fifths of the boat being submerged,” a company representative said. He said the bow of the boat was tied to a large vessel.

“There is a chance that water pouring into the boat through opened hatches may have caused her to sink, although the Navy and police will provide more accurate details,” the representative speculated.

He, however, said there was no one on board at the time of the sinking.

The shipyard, meanwhile, employed a 3,000-ton capacity crane to try to lift the boat, but this failed because of the water in the hold. It said once waves die down divers will go into the submerged ship to pump out water that will allow it to be re-floated more easily.