Crews undertook an almost eight-hour clean-up operation after cooking oil leaked across four miles (6.4km) of the A11.
The road has been shut between Attleborough and Larling, Norfolk, since about 18:30 BST on Saturday.
National Highways said the spillage was cleared by 02:00 on Sunday, but a closure remained in place for emergency resurfacing works.
“The road is expected to be closed for some time to allow this to take place,” it said.
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