A nine-year-old boy was in grave condition in a Vancouver hospital on Tuesday after being buried in sand on a reserve in Kamloops, B.C., on Monday, RCMP said.

The boy was digging tunnels in a sandy bank on the Kamloops Indian Reserve when one of the tunnels collapsed on him, Sgt. Scott Wilson told CBC News.

A girl who was playing nearby at the time went for help but it was unknown how long it took rescuers to arrive, Wilson said.

"A neighbour … subsequently ran across the street and started to uncover or take the dirt off this young boy," Wilson said. "Unfortunately, by the time they actually got him out of there, he was non-responsive."

Emergency personnel on scene were unable to restart the boy's heart and he was taken to a local hospital. He was then airlifted to B.C. Children's Hospital in Vancouver.

The unnamed student, who would have started school at Parkcrest elementary school in Kamloops, remained in grave condition Tuesday afternoon, Wilson said.