A spokesperson for the Navy’s 5th Fleet, which is based in nearby Bahrain, said that a security team aboard the oil supply ship U.S.N.S. Rappahannock fired a .50 caliber machine gun at a “small motor vessel after it disregarded warnings and rapidly approached the U.S. ship” off the coast of Jebel Ali, a city approximately 30 miles from Dubai in the United Arab Emirates.

The Navy is investigating the incident as details continue to emerge. A Navy official said the offending vessel was a white pleasure craft, but a UAE official told ABC News it was a fishing boat with four Indians and two Emirates on board. There doesn’t appear to be any indication the incident was terror-related, the UAE official said.

The Navy official said it’s not uncommon for Iranian speed craft to harass U.S. ships in the region, but in this case the boat wasn’t Iranian.