The U. S. Navy's nuclear submarine USS Jacksonville was damaged early Thursday in the Persian Gulf when one of its two periscopes was struck by an unidentified vessel.

No one was hurt in the early morning incident and the submarine's nuclear reactor did not suffer any damage.

According to a statement from U.S. Naval Forces Central Command, the Los Angeles-class submarine "struck a vessel while operating in the Persian Gulf Jan. 10 at approximately 5 a.m. local time."

The submarine "then surfaced from periscope depth to ascertain if there was any damage to the unidentified vessel. The vessel continued on a consistent course and speed offering no indication of distress or acknowledgement of a collision."

A Navy official told ABC News that it is believed that the submarine had struck a fishing trawler. He said the crew was conducting normal operations "when they felt a shudder, they felt the ship vibrate."

The crew then tried to put up their periscope to determine what had happened, but found it was not working. When they put up the submarine's other periscope they discovered the first periscope "had been sheared off, cut right off," said the official.

Using radar tracks and their periscope observations, the crew determined that a fishing trawler traveling in the opposite direction from the sub was likely responsible for the periscope having been sheared off.

The submarine then traveled by surface to the U.S. naval base in Bahrain, where a damage assessment is underway.

According to the statement, "The reactor remains in a safe condition, there was no damage to the propulsion plant systems and there is no concern regarding watertight integrity."

A P-3 Orion aircraft later conducted an aerial search of the area and saw no debris in the water or an vessels in distress.

The incident is under investigation.