TOKYO (AP) — Coast guard officials searched the office of a Japanese tour boat operator Monday as part of a criminal investigation into suspicions that professional negligence caused the sinking of a vessel carrying 26 people in a national park last month.

The Kazu 1 sightseeing boat started the tour in Shiretoko National Park on the northeastern side of Hokkaido, Japan’s northernmost main island, on April 23 despite forecast rough seas and warnings from other tour operators. It made a distress call that afternoon saying it was sinking.

The Japanese coast guard said investigators were raiding unidentified locations related to the tour boat operator. Footage on NHK public television showed uniformed coast guard officials entering the tour boat operator's office and the house of the sunken boat’s captain.

Separately, the coast guard plans to use a remote-controlled submersible camera to look inside of the sunken boat in hopes of finding bodies possibly trapped inside. The operation was delayed Monday due to bad weather.

The boat carried two crew members and 24 passengers, including two children. Fourteen bodies have been recovered.

The hull of the boat with its name on it was found near Kashuni Falls, where the boat made the distress call. It was upside down on the seabed about 115 meters (377 feet) deep.

The operator, Shiretoko Pleasure Cruiser, had two accidents last year, including one that involved the captain of the sunken boat, Noriyuki Toyoda, the transport ministry said earlier.

Seiichi Katsurada, the head of the company, said last week that he approved the trip despite a broken communication device and forecasts of rough weather. The boat also lacked a satellite phone, he said. Media reports say the captain's cell phone had no signal and the crew borrowed one from a passenger to call the office.

Katsurada said waters at their home port were calm when the boat departed and the captain could have changed the tour plans if the weather worsened.