PORTLAND, Maine (AP) -- Millions of gallons of crude oil from the nation's heartland are crossing Maine in railroad tank cars bound for a Canadian oil refinery, raising concern among environmentalists and state officials about the threat of an accident and spill.
The oil is primarily coming from the Bakken shale-oil field in North Dakota, with lesser amounts from neighboring Canada, where oil production has boomed in recent years. Trains carried nearly 5.3 million barrels of the light crude — more than 220 million gallons — across the state and into New Brunswick last year, and the volume is growing.
Railroads that operate in Maine say the increased business has resulted in more jobs and investment in the state. Moving oil by train is perfectly safe, railroad officials say, with upgraded tracks and modern tank cars.
"The statistics tell you how much has been transported (in Maine), but to the best of my knowledge, there hasn't been any spilled or released," said Robert Grindrod, president and chief executive of Hermon-based Montreal, Maine and Atlantic Railway Ltd., which carried nearly 3 million barrels of oil across Maine last year.
The more oil that's shipped, the greater the likelihood of a spill, said Glen Brand of the Sierra Club. It was fortunate that oil didn't spill into the Penobscot River when a Pan Am Railways oil train derailed March 7 in Mattawamkeag about 100 yards from the river, he said. Only a tiny amount of oil spilled — a state official said it was measured in drips — and Pan Am officials said it likely was residue that had spilled onto the seals of a couple of tank car covers when the cars were filled.
"We got very lucky there that the accident didn't lead to contamination of the river," Brand said. "The more they ship, the more that trains go back and forth, the better the chance there'll be a problem."
What's happening in Maine is happening across the country as U.S. oil production has increased, much of it in areas with limited pipeline capacity. North Dakota oil production doubled between 2010 and 2012.
Because of limited pipeline capacity in the Bakken region, oil producers are using railroads to transport much of the oil to refineries on the East, Gulf and West coasts, as well as inland, according to the Association of American Railroads. The same is true at other shale oil fields that use hydraulic fracturing, or "fracking," to extract oil, the association said.
Five years ago, U.S. trains transported just 9,500 carloads of oil, the association said. The number grew to 65,751 carloads in 2011 before jumping 256 percent last year, to 233,811 carloads.
The mile-long trains bound for the Irving Oil refinery in Saint John, New Brunswick, travel two routes through Maine, typically pulling 80 to 85 tank cars.
Pan Am Railways' trains come through Massachusetts and travel up the same tracks used by the Amtrak Downeaster passenger trains through southern New Hampshire and Maine. They continue into central and eastern Maine before crossing into Canada at Vanceboro and finishing in Saint John.
Montreal, Maine and Atlantic's trains enter the state from Quebec near Jackman in western Maine and travel straight across the state to Canada, also crossing at Vanceboro.
Railroad and state officials said they're aware of only shale oil being transported across Maine and don't know of any so-called tar sands oil coming through.
Environmentalists in the U.S. and Canada have been raising the alarm about the possibility of sands oil from western Canada — which critics call the dirtiest oil on earth — being transported through an oil pipeline that runs through northern New England. The pipeline now carries oil from Portland to refineries in Montreal, but environmental groups say plans are in the works to reverse the flow of the pipeline so thick sands oil can be pumped from Montreal to Portland, where it could be loaded onto ships and taken elsewhere.
The Maine Department of Environmental Protection has concerns about the increasing amount of oil being transported across the state and has begun developing protection plans for the areas where the trains travel, said spokeswoman Samantha Warren.
The department is mapping sensitive natural resources, water bodies, drinking water sources and access points in remote areas, Warren said, as well as developing strategies on how best to respond to spills.
Because each tank car holds some 30,000 gallons of oil, a derailment and spill could be devastating to the environment, she said. But the reality is that the 400,000 home heating oil tanks in Maine pose a bigger threat than the oil trains, she said.
Over the past 15 years, such tanks have spilled oil about 500 times a year adding up to more than 17,000 gallons annually, she said.
Pan Am Railways has spent several million dollars upgrading its tracks in Maine, in large part because of increased traffic generated by oil, said Cynthia Scarano, executive vice president of the Massachusetts-based railroad.
Railroads are simply filling a need, she said.
"The capacity isn't there among pipelines for what we need," she said. "Rather than building new pipelines, we're using something we already have."