The Northstar commuter train had its first breakdown on Sunday, three weeks after it began carrying riders between Big Lake and downtown Minneapolis.

Metro Transit sent two buses to Target Field in Minneapolis to pick up the 120 passengers aboard the 2:05 p.m. train, which never left the station, and take them to the five suburban stations along the Northstar line. The buses left about 3 p.m. and took 90 minutes to reach Big Lake, compared with the train's normal 51 minutes, said Bob Gibbons, spokesman for Metro Transit, which owns the train.

The faulty part was the locomotive's throttle actuator, which sent an incorrect signal that kept the propulsion engine from starting, Gibbons said.

He said a later train Sunday was pulled by a backup locomotive provided by Burlington Northern Santa Fe Railroad, which operates the Northstar for Metro Transit.

Gibbons said the part, covered by a warranty, has been replaced on four of the locomotives. The part is being installed on the remaining, backup locomotive, he said Tuesday evening.

Metro Transit will release ridership figures late this week for the Northstar's first 16 days of operation in November, Gibbons said.

JIM ADAMS