A fishing boat in a recent maritime accident that left seven dead and one missing appears to have sunk into deep sea, the Coast Guard said Wednesday, after a rope that connected it to a tugboat snapped the previous day.

According to the Coast Guard, the 29-ton boat was being pulled by a 190-ton tug vessel when the rope snapped at around 7:06 p.m. Tuesday. Officials searched for the lost vessel for three hours to no avail, and now believe that the boat may have sunk to about 1,000 meters below the surface.

The Coast Guard commenced the search for the lost boat Wednesday.

If the ship is confirmed to have sunk to the bottom of the ocean, officials said it would be practically impossible to salvage, given the depths.

The ship was to be jointly investigated by the Coast Guard and officials from the National Forensic Service and Korea Maritime Transportation Safety Authority.

The fishing boat capsized after colliding with a 456-ton sand barge on Monday in waters near Gyeongju, North Gyeongsang Province, leaving seven of its eight crew members dead and one missing. The seven dead included three South Korean and four foreign nationals, while the missing crew member is of Indonesian nationality.