ANTIOCH -- Fire officials said they are investigating a one-alarm blaze that broke out late Saturday afternoon behind a city pharmacy.

No injuries were reported.

Fire crews were dispatched at 4:08 p.m. to the Rite Aid at 20 East 18th St. for a reported blaze that started behind the building, a Contra Costa County Fire Protection District dispatcher said Sunday.

When crews arrived they learned a fire was set under a truck near the building located near the corner of A Street.

Damages were not known on Sunday, the dispatcher said, and the fire remained under investigation.

Check back for more details.

Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.