The National Park Service is indefinitely suspending visits to the USS Arizona Memorial while engineers study a potential safety issue with its dock.

The park service said today officials noticed bolts connecting the dock to the memorial were stressed.

Visitors may still board boats to the memorial and float past it. They will also be able to see battleship’s remnants. But they won’t be able to disembark the boats and walk on the memorial.

The Arizona Memorial is an open-air structure honoring the 1,177 sailors and Marines killed when their battleship was bombed by Japanese planes on Dec. 7, 1941. The memorial sits above the sunken hull of the vessel in Pearl Harbor.

Visitors ride boats to the memorial from a visitors center on shore.