COPENHAGEN, Denmark (AP) — An oil tanker rammed a Norwegian navy frigate Thursday in a harbor on the country’s western coast, tearing a large hole in its side, the military said. The frigate’s 137 crew members were evacuated amid fears that it may sink.

Eight people on the KNM Helge Instad were injured in the 4 a.m. collision in Sture, north of Bergen, said Rear Adm. Nils Andreas Stensoenes, the head of Norway’s navy. Two of them were taken to a nearby hospital.

The 134-meter (442-foot) long frigate, built in Spain in 2009, is part of a NATO fleet in the Atlantic. The alliance has been informed of the accident, he said.

The Maltese-flagged oil tanker, Sola TS, was not damaged and its 23-man crew remained on board. The shipping site Sysla reported the tanker had been loaded with crude oil and was on its way to Britain.

Stensoenes said the cause of the accident was not clear and the Navy would wait for the findings of Norway’s Accident Investigation Board. Earlier reports had said a towboat was also involved in the collision, but Stensoenes denied that report.

He said the frigate had been pushed by towboats into shallow water where it could not sink fully.

“We are in a security phase for the time being,” he said. He declined to comment on what would happen to the weapons on board the ship.

Some 10,000 liters of helicopter fuel from the frigate has leaked into the sea, said Johan Marius Ly of the Norwegian Coast Guard. The fuel was expected to evaporate quickly.

Norway’s largest oil and gas company, Equinor, formerly known as Statoil, said its non-emergency activities at the Sture terminal where the collision occurred were shut down as a precaution for many hours but were gradually starting up again late Thursday afternoon.

The Accident Investigation Board said because the tanker is Maltese-registered, the Marine Safety Investigation Unit (MSIU) of Malta will participate in the investigation

The Norwegian frigate KNM Helge Instad is in danger of sinking after being rammed by an oil tanker while returning from the NATO Trident Juncture exercise, according to The Associated Press. Images posted by AP show the ship lying on its side in a small cove.

The ship, a Fridtjof Nansen-class vessel, was hit by the Maltese-flagged oil tanker Sola TS around 4 a.m. local time while docked in Sture, north of Bergen, on Norway’s western coast. Eight of the ship’s crew of 137 were injured, and two were taken to a nearby hospital, Rear. Adm. Nils Andreas Stensoenes, the head of the Royal Norwegian Navy, said Thursday during a news conference.

The tanker was not damaged, and its 23-strong crew remains onboard, according to AP.

Norwegian news agency NTB is reporting that the collision tore a hole in the frigate’s side, and that it is taking in more water than can be pumped out.

Stensoenes said the ship was “strongly listing” — or leaning to one side — and that it had been pushed by towboats into shallow water, where it cannot fully sink. He added that the cause of the accident was unclear. Both Norway’s Accident Investigation Board and Malta’s Marine Safety Investigation Unit will investigate the collision, as the tanker was registered in Malta.

The Helge Instad is 442 feet long and was built by Spanish shipbuilder Navantia in 2009. Norway has four other ships of the class in service, which are the Scandinavian nation’s largest naval ships. The ship had recently participated in the Trident Juncture exercise, one of NATO’s largest training events in recent years