South Korea's 1,800-ton diesel-electric submarine in a photo provided by the Defense Acquisition Program Administration (Defense Acquisition Program Administration)A defective inverter module was found to have been the cause of an error message that led to a new 214-class submarine having to be towed in the East Sea earlier this month, Navy officials said Sunday.

The Navy decided to inspect all 214-class submarines to ensure that no such problems would happen again, after finding that a defect was reported in the same part of another submarine of the same type two years ago too, officials said.

The latest incident happened on Jan. 23 when the submarine was in waters off the southeastern port city of Pohang. An error message popped up in the vessel's propulsion system, and officials decided to get the sub towed by a civilian vessel.

The submarine has a total of 12 inverter modules and one of them was found to be defective. It is a key part involved in the spinning of propellers.

"Of the 12 inverter modules, 11 were confirmed to be problem-free, and the submarine moved to the Jinhae naval base on its own for repair," a Navy official said.

The earlier problem happened in October 2019 in the country's second 214-class submarine.

At the time, the Navy sent the defective part to Germany's Siemens for repair, but the problem hasn't been resolved yet, leaving the submarine out of normal operation, officials said.

South Korea has deployed a total of nine 214-class submarines.

"We're carrying out inspections on all of them, but no problem has been found yet," a Navy official said. (Yonhap)