PORTLAND, Maine — One of the Amtrak Downeaster’s daily round-trip trains has been canceled, and other trains in the Boston-to-Maine line have been delayed by maintenance required after federal authorities found problems with the track.

Patricia Quinn, executive director of the Northern New England Passenger Rail Authority, said in a phone interview Tuesday that the Federal Railroad Administration has placed “slow orders” on around 27 miles of Pan Am Railways track — running from the Massachusetts-New Hampshire border to Maine — in about 25 different spots.

“The fact that some are in areas of track where the train [normally] goes 70 mph, it’s really impacting the time,” Quinn said. “It’s hard to tell how long [repairs] are going to take.”

Through this week, Northern New England Passenger Rail Authority has canceled one of its five daily round trips between Portland and Boston’s North Station: the 683 train, which leaves Boston at 11:35 a.m. every weekday, and its 686 train, which leaves Portland at 2:35 p.m every weekday.

Quinn said the railroad authority decided to cancel those trips because delays in its Portland-Boston trip at 2:35 p.m. would bring the train too late to make the 5:40 p.m. return trip from Boston on time. The track safety problems have delayed trains 30 to 40 minutes each way.

That 5:40 p.m. train from Boston, the 687, is one of the Downeaster’s most popular, Quinn said.

“We’ve tried to let people know so they can plan accordingly,” Quinn said.

The service also operates two daily round trips between Brunswick and Boston. The departure times for those trips are not affected by the delays.

Quinn said the timeframe for repairs is uncertain because each track problem detected by the Federal Railroad Administration’s diagnostic “geometry car” last week comes with a different solution. Most of the problems can be attributed to this year’s harsh winter weather.

A representative for Pan Am Railways was not immediately available for comment Tuesday.

For the rail service that so far has reported nearly 25,000 more riders for the first quarter of 2014 than the same period last year, according to the industry group TrainRiders/Northeast, Quinn said she expects the round-trip cancellation will drop its daily ridership by 300 to 400 people.

Darren Fishell

Darren is a Portland-based reporter for the Bangor Daily News writing about the Maine economy and business. He's interested in putting economic data in context and finding the stories behind the numbers.