BNSF Railway says human error caused the Nov. 7 derailment that sent more than 20,000 gallons of ethanol into the Mississippi River near Alma, Wis., while a broken rail has been blamed for a January derailment in Houston County, Minn.

Both derailments remain under investigation by the Federal Railroad Administration.

An accident report that BNSF filed with the agency blames the train operator for applying the dynamic brakes too rapidly, causing 25 cars to jump the tracks.

According to the report, the 112-car freight train was traveling south at 26 mph when it derailed at 8:45 a.m. It carried 20 hazardous material cars, including 15 carrying ethanol. Five of the tankers leaked a combined 20,413 gallons of alcohol.

About 75 people were evacuated and Hwy. 35 closed for about three hours as firefighters from as far away as La Crosse responded.

There were no fires or explosions, but emergency responders said the situation had the potential to be disastrous.

“We dodged a bullet,” said Stephen Schiffli, Buffalo County’s director of emergency management. “It should be a wake-up call.”

Locomotives use electric motors powered by a diesel generator to move trains; those motors can also slow a train with “dynamic braking,” a process similar to downshifting a car. If the dynamic brake is applied too rapidly, momentum at the rear can push forward cars off the track, which one former train operator likened to locking up the front brake on a bicycle.

The BNSF report also blames the train’s make-up, which former train operators say can be a factor when empty cars are followed by loaded ones.

There were no injuries reported in the derailment, which caused about $2.1 million damage to rail equipment and track. Those damages do not reflect the cost of monitoring the Mississippi River, which BNSF is paying for.

About 50 federal, state, and private-sector personnel were involved in the environmental response, and water testing is scheduled to continue through July.

There have been no documented cases of wildlife kills, said Mary Stefanski of the U.S. Fish and Wildlife Service.

Stefanski said responders believe most of the ethanol spilled into the railroad ballast, but long-term monitoring is required to determine whether it is seeping into the water.

A report filed by Canadian Pacific blames “sudden rupture due to over stressed rail” for the Jan. 26 derailment south of Brownsville, Minn.

A railroad spokesman said laboratory analysis of a piece of rail from the scene showed it failed as the train passed over it.

The 68-car train en route from St. Paul, Minn., to Kansas City was traveling 28 mph when 15 cars left the tracks, sending six tank cars and about 660 gallons of vegetable oil into the Mississippi River, according to the report.

Three of the derailed cars were carrying sodium chlorate, a strong oxidizing agent that poses significant health and safety issues when being loaded and unloaded, according to the Environmental Protection Agency. A small amount of the material spilled, though there was not what the EPA calls a "critical breach" and no sodium chlorate was detected in the river, according to the U.S. Fish and Wildlife Service.

There were six additional hazmat cars in the train, but reports do not specify what they were hauling and the railroad has declined to disclose that information, citing “security reasons.”

Wildlife officials noticed a thin sheen of oil on the water after the ice thawed in March but had not documented any harm to wildlife.

In both derailments, the engineer and conductor had been on duty for just short of eight hours, according to the railroad reports. Federal regulations generally restrict crews to 12 hours of duty per day.