Exxon Mobil has asked federal regulators to reconsider a $1 million penalty imposed against the oil giant over a 63,000-gallon crude spill into Montana's Yellowstone River.

The Texas-based company asked the Department of Transportation to withdraw three of its four findings of pipeline safety violations. It also asked for the penalty amount to be reduced.

Safety regulators say Exxon Mobil failed to adequately heed warnings that its 20-year-old Silvertip Pipeline was at risk from flooding.

An Exxon attorney says in the petition for reconsideration filed Feb. 12 that the company was justified in determining flooding was not a great danger after a 2010 risk assessment.

That conclusion proved wrong. The spill left oil along an 85-mile stretch of the Yellowstone, killing fish and wildlife and prompting a cleanup that took months.

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