Two containers fell into the Mississippi River in Wisconsin after a train derailed, the operator said.
CNN  — 

A train derailment in southwestern Wisconsin on Thursday sent two derailed containers into the Mississippi River, and at least four employees were injured, according to officials.

The train derailed around 12:15 p.m. local time near the village of De Soto and all crew members have since been accounted for, according to BNSF Railway, the train’s operator.

They have been treated for minor injuries and released, BNSF spokeswoman Lena Kent told CNN via email Friday.

Two of the three locomotives on the train were involved, along with 10 freight cars. The two cars in the Mississippi River contained nonhazardous materials, she said. Some of the derailed containers which toppled on the shore above the waterline contained lithium-ion batteries and paint, Kent added.

“(A) boom has been placed in the area as a precautionary measure, but the volumes involved don’t pose a risk to the river or nearby communities. BNSF personnel are on the scene and working closely with local and state agencies,” the statement said.

The cause of the incident is still being investigated. The main track is still blocked in both directions with no estimated time for the reopening, the statement added.

Video taken by witness Caitlin Nolan and other images on social media show some of the train cars in the river.

“It was reported to us that there were hazardous materials on the train itself, but it is not believed to be a concern to the public or the responders at this time as those cars were contained,” Marc Myhre, a Crawford County emergency management specialist, said during a news conference.

Hazardous materials crews remained on the site as a precaution Thursday evening since some of the cars not in the river contained lithium-ion batteries, which can have a chemical reaction if they come into contact with water, Vernon County emergency management director Brandon Larson said. The train was also carrying oxygen containers, which can be explosive if not maintained properly.

Recovery work is shown at the scene of a train derailment on Thursday in Wisconsin's Crawford County.

The derailed units were two of the train’s three locomotives and “an unknown number of cars carrying freight of all kinds,” BNSF said.

Heavy rain has recently brought parts of the Mississippi River to near flood stage, but the railroad tracks at the site of the derailment were above water, Myhre said.

The derailment happened at about 12:15 p.m. Thursday, BNSF said.

US Rep. Derrick Van Orden, who represents the area, said his office was coordinating with state officials, BNSF and the Federal Emergency Management Agency to “get answers on what occurred.”

The congressman’s staff was traveling to the site of the derailment and will “continue to monitor the situation and determine next steps,” his statement reads.

CNN’s Pete Muntean, Andy Rose, Jennifer Henderson and Kara Devlin contributed to this report.