NORFOLK, Va. >> The Pentagon said that it is investigating why a Navy submarine collided with an Aegis cruiser during routine operations at an undisclosed location.

The U.S. Fleet Forces Command said in a news release that the submarine USS Montpelier and the Aegis cruiser USS San Jacinto collided at about 3:30 p.m. Sunday. No one was injured, and the extent of any damage to the vessels was not clear Saturday evening, said Lt. Commander Brian Badura of the Fleet Forces Command.

"We have had circumstances where Navy vessels have collided at sea in the past, but they’re fairly rare as to how often they do take place," Badura told The Associated Press.

Navy officials said the collision was under investigation, but declined to offer specifics on what happens next or on where the incident took place.

"If we do have an incident that does take place, there are folks that swing into action… to help us make a better, more conclusive explanation of exactly what happened," Badura said.

The news release says "overall damage to both ships is being evaluated," and that the sub’s propulsion plant was "unaffected by the collision." Both Navy ships are based at Norfolk, Va. and are operating on their own power, the news release says.

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Associated Press writer Norman Gomlak contributed to this report from Atlanta.