ROCKLAND, Maine — The state is seeking proposals from companies to operate the railroad line that runs from Brunswick to Rockland.

The proposals are to include bids on possible year-round passenger service from Rockland to Brunswick to connect to the Amtrak trains.

For the past two years, the state has been discussing whether to seek new competitive proposals to operate trains on the 58-mile route.

Maine Eastern Railroad has run the line since 2003. Its contract with the state was set to expire in October 2013, but the company and state reached an agreement to have Maine Eastern Railroad continue its operations.

Maine Eastern Railroad carries freight year-round and a limited passenger excursion service during the summer. The company receives no state subsidy and is required to maintain the tracks.

Nathan Moulton, director of the rail program for the Maine Department of Transportation, said the requests for proposals are intended to determine what interest there is in continuing freight transportation and perhaps expanding passenger service.

He said any regularly scheduled passenger service to connect Rockland to Brunswick would likely require a state subsidy to an operator. Moulton said the department wants cost estimates from bidders on the amount of subsidy that would be needed.

“Then when people say they would like to see passenger rail service extended to Rockland, we will be able to say, ‘It would cost this much,’” Moulton said.

The requests indicate that the operator would carry freight along the line and be responsible for maintenance of the tracks.

Proposals must be submitted to the transportation department by Aug. 13.

“Maine Eastern Railroad will be placing a bid on the state’s [request for proposals], with the hope to continue operating the Rockland branch for both freight and passenger service,” Maine Eastern Railroad General Manager Harmony Llanto said Friday in a prepared statement. “We currently are not in a position to share all the details in our plans, however we do plan to expand our passenger service to better service the communities along our route.”

The line has been operating for freight traffic since May 1990, five years after Maine Central Railroad abandoned the spur. The state spent $30 million in the early 1990s to upgrade the tracks to be able to handle passenger trains, which resumed running on the Rockland line in 2004.

Passenger service during the past 10 years has been limited largely to summer excursion trips. The amount of traffic peaked at nearly 19,000 people in 2008, according to prior statements by Maine Eastern Railroad.

The largest source of revenue for Maine Eastern Railroad has been its freight service, and Dragon Products is by far its largest customer.

Another customer of Maine Eastern Railroad is Dica Perl Minerals, formerly known as Chemrock, on Buttermilk Lane in Thomaston. Maine Eastern Railroad also does some business with Bath Iron Works.