Sonar used by the Japan Coast Guard has detected what appear to be several sunken ships in an area off Hokkaido’s Shiretoko Peninsula where a tour boat disappeared, coast guard and local officials said Tuesday, a day after the death toll from the incident rose to 11.

The JCG said objects that appear to be vessels have been detected in various locations, including at a depth of around 30 meters, but it could not determine whether the readings were connected to the 19-ton Kazu I, which went missing off Japan's northernmost main island on Saturday with 26 aboard, including two crew members.

Four JCG divers started searching the area where the boat issued its first rescue call but had to suspend the operation due to high waves.