Railroad construction in Southern Maine and New Hampshire will disrupt passenger rail service from the Amtrak Downeaster starting this weekend through early October.

Weekday service between Brunswick and Dover, New Hampshire, will be limited and passengers on most of the line should expect to take part of their trip by bus, said Patricia Quinn, executive director of the Northern New England Passenger Rail Authority. Weekend service will operate normally, but there will be construction delays, Quinn said. Most fares have been reduced during the construction period.

Pan Am Railways is replacing about 15,000 railroad ties and restoring a number of grade crossings on its line in Maine and New Hampshire. Construction is expected to begin on Saturday, Sept. 8 and wrap up by Oct. 5.

Passengers disembark from the Amtrak Downeaster in Boston.