The USS Arizona Memorial at Pearl Harbor was closed down after a civilian tug assisting the Navy hospital ship USNS Mercy out to sea apparently hit the memorial’s floating dock around 7:45 a.m. Wednesday, according to Navy officials and media reports.

“The floating dock at the USS Arizona Memorial in Pearl Harbor was damaged this morning as the hospital ship USNS Mercy was underway,” Navy Sector Hawaii reported on its Facebook page.

“Initial reports indicated that a tug boat hit the memorial, but an investigation is underway. White boat passenger traffic onto the memorial has to be suspended as we assess the full extent of damage and can ensure the safety of visitors.”

Boat tours of Pearl Harbor are continuing from the visitors’ center, but passengers won’t be able to get onto the memorial while the National Park Service and Navy investigate and assess the damage. Up to 5,000 people tour the harbor daily, according to the Park Service.

The incident was first reported by quoting witnesses who described crunching and scraping noises as the ship and tug passed close by the memorial.

The memorial remembers the 1,177 sailors and Marines who died on the battleship when its forward ammunition magazine was detonated by a Japanese bomb during the surprise attack of Dec. 7, 1941 that led America to war. It was the single biggest loss of life during the air raid, and most bodies were never recovered from the ship’s sunken hull, straddled by the memorial built in 1962.

The Mercy got an overhaul this winter at Vigor Industries’ Swan Island dry dock on Oregon’s Willamette River, and was departing Pearl Harbor for the Navy’s recurring "Pacific Partnership" humanitarian mission that brings advanced medical care to island nations and Southeast Asia. This year’s mission includes stops in the Philippines and Vietnam, Papua New Guinea, the Solomon Islands, Kiribati, and islands of Micronesia.