ANTIOCH -- A 9-year-old Oakley boy was critically injured Saturday after colliding with a 15-year-old boy as the pair rode their dirt bikes on an Antioch dirt lot, police said.

Despite both boys wearing appropriate protective gear and helmets, the younger boy had major head trauma and was flown to Children's Hospital in Oakland, according to Antioch police Sgt. Robert Quintero.

The boys were riding on separate off-road motorcycles around 1:46 p.m. Saturday in a dirt field at the end of Drive In Way in Antioch with adults on scene providing supervision, Quintero said. After the collision, the Antioch teen only had a complaint of pain, but a parent rushed the seriously injured younger boy to Sutter Delta Medical Center where he was stabilized before being flown to Oakland, police said.

Police are not naming the boys because of their age.

The collision is under investigation, Quintero said.

Anyone with information can call Antioch police at 925-778-2441. Anonymous tips can be texted to 274637 (CRIMES), using the key word "ANTIOCH."

Contact Matthias Gafni at 925-952-5026 or mgafni@bayareanewsgroup.com. Follow him at Twitter.com/mgafni.