The M11 in Essex was closed for 18 hours overnight and into the following morning after a lorry overturned and spilled chemicals across both carriageways.
It happened at around 5pm Thursday, during the rush hour. The road was shut between junction 7 and 8 between Harlow and Bishop's Stortford near Stansted Airport.
Drivers were left stranded as an exclusion zone was set up by the Fire Service to protect people from possible toxic fumes.
The spilled chemicals were identified as phosphoric acid and melamine formaldehyde resin.
Phosphoric acid is commonly used in fertilisers, food additives and home cleaning products, as well as in medicine and dentistry to help whiten teeth.
The M11 re-opened at around 11am after being closed for about 18 hours in total.