The accident was reported shortly after 10 p.m. near Arrow Highway and Walnut Avenue, the Fire Department said. The rear end of the truck, which was empty, was hit by the train.
Firefighters were at the scene inspecting the train and checking passengers. Metrolink said on its Twitter account that San Bernardino lines 336 and 339 were stopped between Covina and Pomona because of the accident.
No other details were immediately available.