WALLA WALLA -- A Washington State Department of Ecology spokesperson is updating the estimate of how much diesel fuel spilled near the Columbia River when a Union Pacific freight train derailed early Wednesday morning, south of Wallula.

Stephanie May, a communications manager for the department, said it is now estimated that about 1,400 gallons of diesel was spilled in the incident.

The earlier estimate was about 660 gallons. No injuries were reported in the derailment.

May said cleanup efforts are going well.

"Cleanup contractors have placed two layers of containment booms around the spill, and that's trapping that oil in place against the riverbank," she said. "We're currently not observing any sheening outside of that boomed area. So, the goal right now will be to remove the oil from within that containment boom."

Investigation into the cause of the derailment is still ongoing, May said.

The train derailment occurred about 3:30 a.m. The Department of Ecology was informed about 4 a.m., but the spill was not immediately detected. At 6:30 a.m., the department was informed that the derailment caused a spill, and cleanup efforts began shortly after.