A trucking firm in Wisconsin is claiming that fuel-filter problems plaguing its trucks may have been caused by soybean-based biodiesel purchased from a Minnesota supplier.

The Milwaukee Journal Sentinel reported that Valley Cartage, a trucking company in Hudson , WI , began having problems with clogged fuel filters just days after it switched to biodiesel in all of its trucks.

The company, which has 50 trucks, said the problems worsened in cold weather. Tom Chrismer, vice president of Valley Cartage, told the Journal Sentinel that his company changed 50 fuel filters on its trucks in a month.

The biodiesel was purchased from a supplier in Minnesota , according to the Journal Sentinel.

Minnesota has been seeing its own share of fuel filter problems since switching over to a mandatory 2 percent biodiesel blend in October 2005.

Minnesota temporarily suspended its biodiesel mandate while investigators try to determine the reason for the problem. The suspension is scheduled to run out Friday, Jan. 13.

The actual cause of the fuel-filter problems has yet to be determined.

Meanwhile, the Journal Sentinel reported that Valley Cartage has switched back to straight diesel and has not had any further fuel-filter issues.