A U.S. nuclear submarine collided with a merchant ship while operating in the Persian Gulf, the U.S. Fifth Fleet said in a statement, according to RIA Novosti.

“No one was hurt when the periscope on USS Jacksonville (SSN 699), a U.S. Navy Los Angeles-class submarine” hit the unidentified vessel around 5 a.m. local time on Thursday, the U.S. Navy said.

According to the U.S. officials, the Jacksonville surfaced from periscope depth to check whether there was any damage inflicted on the unidentified vessel, which “continued on a consistent course and speed offering no indication of distress or acknowledgement of a collision.”

A U.S. P-3 Orion maritime patrol aircraft conducted a search of the area and spotted “no debris in the water or vessels in distress.”

One of the submarine’s two periscopes suffered minor damage. The incident is under investigation, the Navy said.

The waters of the Persian Gulf are relatively shallow (average depth 150 feet or 50 meters) and can sometimes be a difficult environment for operating large attack submarines, especially when large numbers of surface ships are present, according to naval officers who have operated there.

In August, the U.S. Navy said one of its guided missile destroyers had collided with a Japanese-owned oil tanker in the Strait of Hormuz. No one was injured.