A pipeline breach in Montana dumped 50,000 gallons of oil into the Yellowstone River on Saturday, prompting the governor to declare a state of emergency.

Residents in nearby cities were told to not drink the tap water, which some said smelled like diesel.

According to the Bridger Pipeline Co., the massive oil spill occurred around 10am Saturday morning when the 12-inch pipeline, which crosses the Yellowstone River, ruptured about five miles upstream from Glendive. And while it seems that up to 1,200 barrels - or 50,000 gallons - of oil managed to get into the water, the affected site was luckily mostly frozen, helping to reduce the impact on both local residents and wildlife.

"We think it was caught pretty quick, and it was shut down," Dave Parker, a spokesman for Gov. Steve Bullock, told The Associated Press (AP). "The governor is committed to making sure the river is cleaned up."

It only took about an hour after the initial breach for the Bridger Pipeline Co. to shut down the pipe; however, it's still possible that oil got trapped by sediment and debris and settled into the riverbed, possibly impacting birds, fish and other wildlife near the river.

"Our primary concern is to minimize the environmental impact of the release and keep our responders safe as we clean up from this unfortunate incident," said Tad True, vice president of Bridger.

Officials are still waiting for results from water sample testing, CNN reports, and until they come in residents are urged to use bottled water for drinking and cooking.

Remarkably, this isn't the first time a major oil spill has occurred in the Yellowstone River - the longest undammed river in the United States. Just in 2011, an Exxon Mobil Corp. pipeline burst near Laurel during flooding, sending about 63,000 gallons of oil into Yellowstone waters that later washed up along an 85-mile stretch of riverbank.

Even after spending a staggering $135 million on the aftermath, the company is currently facing state and federal fines of up to $3.4 million from the spill.

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