The Navy said Wednesday it is investigating a recent accidental discharge of a torpedo from a frigate during an exercise in the Yellow Sea.

According to the Navy, a 2,300-ton frigate called Cheongju accidentally fired a deactivated torpedo during a drill in waters off Taean, South Chungcheong Province, last Thursday. The Navy said the torpedo didn't explode and sank to the bottom of the water.

"We believe there was some malfunctioning to the hydraulic system," a Navy official said. "We're looking for the exact cause of the case."

The torpedo was the homegrown anti-submarine missile named the Cheongsangeo, or Blue Shark. About 2.7 meters long and weighing 280 kilograms, it can travel at up to 45 knots, or 83 kilometers per hour. In December 2009, another Blue Shark torpedo was accidentally fired during an anti-submarine exercise. (Yonhap News)