Crews have started removing contaminated soil and damaged railcars left behind by Thursday's fiery derailment in southwest Minnesota.

Authorities said Friday afternoon the ethanol fire that burned for hours had been extinguished and that local firefighters were allowed to leave after remaining on site overnight. But large water tanks and railroad firefighting equipment remained at the site to handle any flare-ups as damaged tank cars are removed.

The entire town of Raymond, which is about 100 miles (161 kilometers) west of Minneapolis, had to be evacuated after 22 cars, including 10 carrying ethanol, left the tracks. Four of the tank cars ruptured and caught fire. But the several hundred residents were allowed to return home by midday Thursday, and no injuries were reported.

This latest derailment only adds to concerns nationally about railroad safety. Lawmakers and regulators want freight railroads to make changes after last month's derailment near East Palestine, Ohio, that forced half that town to evacuate. Even though officials say the area is safe, many residents have lingering health concerns.

The Kandiyohi County Sheriff's office said BNSF railroad crews began removing some of the contaminated soil under and around the tracks early Friday morning. And once investigators from the National Transportation Safety Board gave the OK, workers started to remove the damaged railcars.

It’s not clear how long the cleanup will take, and no cause of the derailment has been determined yet.

The head of the Fort Worth, Texas-based railroad promised a thorough cleanup and said BNSF works hard to prevent derailments like this from happening.

NTSB spokesman Keith Holloway said the BNSF train had three crew members — an engineer, conductor and brakeman — aboard when it derailed around 1 a.m. Thursday. The train had a total of 14 ethanol cars along with corn syrup it was delivering.

Holloway said investigators will work to determine what caused the derailment.

The Environmental Protection Agency continued monitoring the air around the derailment Friday, but officials said the agency hasn’t found any worrisome levels of contaminants or particulate matter.