Oil swirls in a flooded gravel pit in Lockwood, Mont. after a pipeline break early Saturday.
Exxon shares saw a minor hit on Tuesday following the accident.
"I didn't feel like this was a huge event," said Philip Weiss, oil and gas analyst at Argus Research, who characterized the stock's 0.5% dip as reasonable and said that he wasn't surprised.
The Yellowstone River spill would only exacerbate issues for Exxon shares if it became a repetitive problem, according to Weiss.-- Written by Joe Deaux in New York.
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