A 12-year-old boy from Arizona was seriously injured early Wednesday morning when a tree fell and crushed a tent where he was sleeping in a San Mateo County park.

Just before 5 a.m., firefighters and park rangers responded to a report of a fallen tree in a camping area at Memorial Park near Pescadero, San Mateo County sheriff's Lt. Larry Schumaker said.

A tree between 40 and 60 feet tall and more than a foot in diameter fell onto a tent where two 12-year-old boys were asleep, Schumaker said.

The boys were camping with relatives, all of whom were on vacation from Arizona, Schumaker said.

One of the boys was crushed by the trunk of the tree and taken by ambulance to Lucile Packard Children's Hospital at Stanford.

The other boy suffered minor cuts and bruises, and no one else was injured.

The incident remains under investigation.