MISSOULA, Mont. -

North Dakota oil fields are booming and millions of barrels of crude oil are headed to market, but refineries are hundreds of miles away, and railroads carrying the oil admit their volatile cargo has become "a threat" to the communities they pass through.

Even the release of general data about the size and number of trains had Burlington Northern-Santa Fe officials pleading with the State of Montana to keep the information confidential.  They called the data "sensitive security information."

Montana refused to sign the confidentiality agreement.  Instead, the State published the reports on the DEQ's internet portal.

What the reports reveal is a steady stream of Bakken oil is passing through Montana, on its way to west coast refineries.  The numbers are huge and shippers indicate they'll continue to grow.

Initial reports show at least nine trains a week passing through Whitefish on the BNSF primary route, each train with one hundred cars or more.  That's an estimated 27 million gallons of Bakken crude.

Montana Rail Link's southern route through Montana sees three trains a week.  Each train carries an estimated 3 million gallons, bringing the southern route total to an estimated 9 million gallons.

The exact size of the trains is difficult to determine.  Most unit trains leave North Dakota with 100 tank cars or more.  The U.S. Energy Information Administration estimates each car is carrying 30,000 gallons of oil.  The reporting requirements only call for a tally of trains carrying more than a million gallons, not the number of cars or the tank car capacity.

Under to reporting procedures, rail carriers are required to notify each county they pass through.