The brutal cold — not increased freight traffic — has been the primary cause of delays on the Northstar commuter line between Elk River and Minneapolis, a BNSF railroad spokesman said Thursday during a legislative hearing.

Legislators called the hearing in hopes of getting answers to why the commuter line has been disrupted repeatedly over the past two months.

“Weather has created havoc,” said Brian Sweeney, the railroad’s regional assistant vice president, state government affairs, noting that the run of subzero temperatures has caused switches to freeze up several times and tracks to become brittle. “Crews can only work outside for 20 minutes at a time. That affects one train, and then there’s a ripple effect. We’ve seen that on Northstar. … Oil traffic is not a factor.”

Sweeney said BNSF said delays began with the arctic chill in January.

The cold has meant that freight trains have had to run at slower speeds and trains have fewer cars. That in turn has increased the number of trains, taxing the tracks’ capacity, Sweeney said.

The agreement between BNSF and Metro Transit stipulates that 95 percent of all Northstar trains should be dispatched to arrive at their terminal station within five minutes of their scheduled arrival time each month. Since January, that figure is down to about 75 percent, Metro Transit General Manager Brian Lamb said.

In response to the frequent delays and rising customer furor, Metro Transit this week dispatched emergency buses to two of its busiest rail stations, Elk River and Coon Rapids, to handle passengers if trains were delayed. On Monday, some trains were delayed up to two hours and Metro Transit told its customers to find other modes of transportation.

A few weeks ago, Metro Transit started sending e-mails and text messages to 700 riders who subscribed to a new rider-alert program.

“That shows the desperation that our customers are feeling,” Lamb said. “Employers only have so much patience.”

Is cold really the cause?

Lamb questioned whether the cold was the real reason for delays. He noted that Northstar trains ran on schedule Tuesday, Wednesday and Thursday even with temperatures in the teens below zero.

Thursday’s hearing yielded no solution. Sweeney said that he hoped things will get better when the weather improves.

“We’ve brought in crews from other parts of the system and added locomotives to try to keep current,” Sweeney said. “Reliability is critical to have a commuter-rail operation. We need to win back confidence.”

Until January, when the delays began, Northstar had a 96 percent on-time record. Metro Transit spokesman Drew Kerr said the number of rides on Northstar in January was down 2 percent to 54,507 compared with January 2013. The bitter cold and school closings also were factors in the decline, Kerr said.

Legislators said they will continue to assess the situation and reconvene if necessary.

“We still want to get to the bottom of this and prevent this from happening in the future,” said House Transportation Finance Committee Chairman Frank Hornstein, DFL-Minneapolis.