Police investigators Monday visited the scene of an unsolved home-invasion murder of a family of four in Tokyo that they think took place either late Dec. 30 or early Dec. 31, 2000.

To mark the 13th year since the brutal stabbing deaths of Mikio Miyazawa, 44, his wife, Yasuko, 41, their daughter, Niina, 8, and son, Rei, 6, Metropolitan Police Department investigators laid flowers in front of the family’s home in Setagaya Ward, which remains unoccupied.

“We will resolve this case with all our might and arrest the culprit,” said Tatsuya Aoki, the MPD investigator in charge of the case.

The ceremony was held as part of the MPD’s efforts to keep public awareness of the case alive.

A gray sweat shirt with purple raglan sleeves and neck were found in the house among other pieces of evidence. Previous reports said police believe the killer suffered a deep wound to the hand, based on blood and other evidence found at the scene.