A South Korean man is suspected of triggering an explosion in a restroom at the Yasukuni Shrine, which honors Japanese war dead, in Tokyo last month, Japanese news reports said Thursday, citing police officials.

Mainichi Shimbun reported that an investigation is underway after the police found that a South Korean man in his 30s appeared in the footage of a surveillance camera installed near the restroom right after an explosion that caused no casualties.

In the footage, he was seen wandering around the shrine some 30 minutes before the sound of an explosion was heard, reports said. After the incident, he immediately moved to a hotel in Chiyoda and then left the country.

Following the explosion, four pipes that were tied together with tape were found. There was gunpowder inside the pipes, reports said.

The shrine, considered a symbol of Japan’s past imperialism, houses the remains of 14 Class A war criminals from World War II. Conservative Japanese politicians have visited the shrine despite criticism from South Korea and China, two major victims of Japan’s past militarism.

During a regular press briefing, Japan’s Chief Cabinet Secretary Yoshihide Suga refused to confirm that a South Korean man was involved in the incident. Instead, he said that all investigation procedures would proceed “in accordance with the law and hard evidence.”

By Song Sang-ho (sshluck@heraldcorp.com)