MOSIER, OR -- Clean up continues in the Columbia River Gorge, after an oil train derailed and exploded Friday, near the small town of Mosier. Evacuations were lifted late Sunday; However, a boil water order remains in effect for residents, due to concerns over wastewater contamination near the crash site.

Officials with Union Pacific and the federal government are investigating how the train crashed. One official told reporters at a weekend press conference, "We absolutely want to know what happened, because we want to prevent it from happening again."

A small amount of oil reached the Columbia River, creating a sheen about six feet from shore. It was contained by a boom, and officials are looking into how it got there, "Probably sub-surface, potentially through a spring or potentially through a nearby sewer treatment plant."

Some of Oregon's Congressional delegation say the train derailment is an example of what they're trying to prevent with new Legislation. Senator Ron Wyden issued a recorded statement saying, "It is clear with this crash, as it has been for years, that more must be don’t to protect our communities from trains carrying explosive hazardous fuels." Wyden added, "That’s why I’ve repeatedly called for more resources and notifications for first responders, and why I’m continuing to push for my bill to move unsafe cars off the tracks and away from our communities." He and Rep. Earl Blumenauer (D-OR) have been working to increase resources for fire departments along rail lines, and promote the use of tanker cars capable of withstanding a derailment with less risk of a rupture and fire.