PHOENIX (AP) _ A construction worker on a project to demolish a downtown parking garage was trapped early Tuesday when concrete collapsed onto his tractor, officials said.

The worker was conscious and talking but was seriously injured, with tons of concrete pinning his legs inside his front-end loader, said Mike Sandulak, a division chief with the Phoenix Fire Department.

Firefighters used wooden shoring and air bags to stabilize the building to prevent further collapse, and were working to cut reinforcing bars in the concrete to remove it, Sandulak said.

He said there was no estimate on when they may be able to free the worker.

Firefighters gave the unidentified 28-year-old worker pain medication and started intravenous lines so they could give other medications and fluids, Sandulak said.

The accident happened about 4:45 a.m. during demolition work at the Civic Plaza construction site in downtown Phoenix.