The 406 closure in St. Catharines will continue into late this evening.
Emergency crews had hoped to reopen the stretch of the highway northbound, between Glendale and Westchester, this morning, but the clean up is still underway.
A tractor trailer hauling 9,000 kilograms of hydrochloric acid started to fall apart on the 406 in the northbound lanes at 12:30 yesterday afternoon.
The driver pulled over right away, and acid started to leak onto the roadway.
Acid has also been found in the ditch area.
OPP Sergeant Kerry Schmidt joined CKTB's Tom McConnell with an update saying he doesn't except the northbound lanes to reopen until beyond sunset.
The clean up crews are on scene, along with the Ministry of Environment.
It's unclear if the road can be repaved or if it needs to be completely replaced as the acid eats into the asphalt.
The southbound lanes were reopened during the overnight hours.
That stretch of the 406 is busy as it sits next to the Pen Centre Mall.