Part of a human skull has been found near a mountainside campsite in Yamanashi Prefecture, west of Tokyo, where a 9-year-old girl went missing over two and a half years ago, investigative sources said Tuesday.

Police are working to determine if the remains belong to Misaki Ogura, from Narita, Chiba Prefecture, who disappeared shortly after arriving at the campsite in the village of Doshi with her family in September 2019.

According to the prefectural police, a man in his 40s found the remains on the side of a mountain trail around 600 meters east from the campsite on Saturday, reporting it to the police in the village two days later together with a photo.

An autopsy performed Tuesday identified the bones as part of a human skull. The police searched the area with a team of 40 the same day, and plan to continue in the days ahead.

Ogura went missing after eating snacks near a tent around 3:40 p.m. on Sept. 21, 2019, as she followed other children heading to another spot.

Her mother, Tomoko, and the prefectural police have appealed to the public for any information, but no promising leads have been found. The 39-year-old mother tweeted Tuesday that she believes "Misaki will come home safely."