The transportation of propane gas into Maine is part of a complex system that has been strained by a railway strike in Canada.

Workers at Canadian National Railway Co. remain on a strike that began Feb. 10 and which has severely cut the amount of propane entering the state from the north.

About 33,000 households in Maine rely on propane gas to heat their homes, according to the Public Utilities Commission. Numerous businesses use propane to cook, heat buildings and for other commercial uses.

Propane gas comes to Maine via two methods of transportation: rail and truck. Maine does not contain any pipelines that distribute propane gas, according to the PUC.

Sixty percent of Maine’s propane arrives on the Canadian National Railway from Sarnia, Ontario. Forty percent of Maine’s propane is delivered by truck from a port in Newington, N.H., near Portsmouth. In recent weeks, propane has been driven up from Providence, R.I., and Selkirk, N.Y.

Hermon and Auburn are the hubs for rail and truck deliveries from out of state. Delivery trucks for oil and fuel companies across the state arrive in Hermon and Auburn to pick up propane and distribute it to their local homes and businesses.

On a normal winter day, residential and commercial customers consume roughly 500,000 gallons of propane, according to Jamie Py, president of the Maine Oil Dealers Association.

Even with distributors curtailing fill-ups by providing only partial deliveries, Mainers still are consuming 300,000 to 400,000 gallons daily, Py said.

“Things look good, but dealers say we can’t look ahead more than a few days. We never know how much we’re going to get or when it’s coming,” Py said.

As many as 75 Canadian rail cars, carrying up to 30,000 gallons each, arrived Tuesday in Maine to alleviate the shortage. The rail cars were brought to Maine by a short-line partner of Canadian National.

But with relief came more complications. The pipeline that carries propane from the Gulf of Mexico to Selkirk, N.Y., ruptured Tuesday, Py said. The pipeline is still operating but not at normal pressure, he said.

A sea tanker that can carry 16 million gallons is expected Thursday or Friday in Providence, R.I., and another is due at Newington, N.H., on March 6.

“There are so many wildcards that could change this thing daily,” Py said.