The Monash Freeway has reopened after a day of traffic chaos sparked by a chemical spill.

The freeway was closed in both directions on Wednesday morning after the chemical spill involving a drum of leaking aviation fuel.

The freeway was clogged after the road closed in both directions between Heatherton, Endeavour Hills and Stud roads, Dandenong North about 10.50am.

VicRoads said the freeway between Stud Road and Belgrave-Hallam Road reopened at 3pm in both directions, however heavy delays were still expected.

"Although the freeway is now open, drivers need to be prepared for ongoing delays," VicRoads Director of Road Operations Dean Zabrieszach said.