NEW : An ExxonMobil official says oil detected 25 miles away ; the state says 25 miles . While no official determination has been made on what caused the pipeline rupture , the governor said it is easy to see the dangers posed by fast-moving waters . Montana declares a state of emergency for seven counties , says ExxonMobil is responsible . Company officials remain unclear of the cause of the spill in Montana 's the Missouri River . ExxonMobil reports up to 42,000 gallons of oil -- 90 miles -- escaped through a crack .
NEW : An ExxonMobil official says oil detected 25 miles away ; the state says 25 miles . Montana declares a state of emergency for seven counties , says ExxonMobil is responsible . Company officials remain unclear of the cause of the spill in Montana 's the Missouri River . ExxonMobil reports up to 42,000 gallons of oil -- 90 miles -- escaped through a crack .