The fire that caused the collapse of a heavily-used rail bridge near Ericsburg, Minnesota on Wednesday was "accidental in nature," the Koochiching County Sheriff reports.
A multi-agency investigation also "produced evidence" that there had been a mechanical failure in the incident, but a release from the Sheriff did not elaborate any further.
Meanwhile, rail traffic that relies on the important Canadian-American border crossing is at a standstill while engineers build a temporary replacement bridge, MPR News reports.
The station says the bridge was the "second busiest rail border crossing" in the U.S.
No injuries were reported, but there was significant destruction.
At last report, crews were building a crane to remove the downed cars from the Rat Root River.