An explosion on Monday at the Yasukuni Shrine in Tokyo caused damage to a public bathroom, but did not injure any of the occupants.

The walls and ceiling of the bathroom were charred, but an official from the Tokyo Fire Department said that by the time they got there, the fire had already burned out, according to the Independent. The rest of the shrine was undamaged.

The blast went off around 10 a.m. local time, just before a ceremony celebrating the autumn harvest was about to commence. There were about 120 people in the shrine at the time of the explosion, according to the Wall Street Journal. Despite the presence of the patrons, no one was injured.

A person who was near the main gate of the shrine heard the explosion and saw smoke inside the washroom and immediately called the police, according to Reuters. Investigators later found remnants of wire and some batteries nearby, and a bomb squad was called to the scene to investigate.

While no suspects have yet to be apprehended, it is possible that the incident might have been politically motivated. The shrine has been a source of controversy, with some claiming that the shrine glorifies Japan's historical militarism.

The shrine commemorates those who died in service of the empire. Among the 2.4 million who are commemorated in the shrine are the names of over a thousand war criminals, including several "Class-A" war criminals.

The recent incident is not the first of its kind to take place at the shrine. In 2011, a Chinese citizen, Liu Qiang, set fire to one of the gates for politically-motivated reasons. He claimed that his grandmother had been captured by Japanese soldiers and made to work as a sex worker in China, according to the Global Times. His grandfather was also involved in fighting the Japanese army.