A tanker truck hauling diesel fuel overturned after it was “bumped,” by a freight train in the Union Pacific rail yard early Friday morning, a railroad official said.

The rail yard is in the area of East 22nd Street and South Campbell Avenue.

The tanker, which has a 5,000 gallon fuel capacity, was struck at about 4 a.m., Capt. Barrett Baker, spokesman for the Tucson Fire Department, said. The department is helping Union Pacific with clean-up.

About 1,000 gallons of diesel spilled from the truck, which is used for re-fueling vehicles in the rail yard, Aaron Hunt, a Union Pacific spokesman, said.

Containment booms have been set up around the spill to keep the fuel from spreading and to absorb some of the diesel, Hunt said. Once TFD removes the remaining fuel from the tanker, the truck will be moved out of the way and Union Pacific can continue clean-up.

“Any fuel that hasn’t been soaked up by the boom or the other sand and materials we put in the area, we’ll vacuum the up with a truck,” specially designed to suck up spilled liquids. After that, the railroad’s hazardous materials team will take soil samples to determine how much fuel was absorbed into the ground and how much soil must be removed.

“Thus far, from everything my team on the ground is telling me, none of the fuel on the ground has made contact with a water source,” Hunt said.

He expects freight trains to begin running through the yard again no later than tonight. The train involved in the collision has already departed for its destination in Phoenix, but two other trains are being held in the yard pending the removal of the tanker.

The driver of the truck was taken to the hospital for observation.