Three people have been taken to hospital following the incident involving an overturned tanker on the M56 .
The three casualties, including the lorry driver, were taken by ambulance to the Countess of Chester Hospital with complaints of skin irritation.
The tanker is understood to have be carrying a significant amount of cresol (chemical 2810) – a hazardous, but non-explosive substance, which has leaked out onto the carriageway.
Exposure to cresol can result in strong skin irritation, throat irritation and nasal constriction.
A further five casualties with minor injuries were treated at the scene and were not taken to hospital.
The M56 in Cheshire between Junction 11 and 14 is not expected to reopen in both directions until Wednesday morning at the earliest and two miles of tailbacks remain since around 4pm on Tuesday afternoon.
Cheshire Police are unable to confirm what time the road will be reopened.
Emergency services are still at the scene and are awaiting the arrival of the recovery vehicle.
Central reservations on the M56 have been removed to enable cars to start moving.
A spokeswoman from Cheshire Police said emergency services are doing all they can to free traffic as soon as possible.
Abandoned vehicles remain at the scene along with the overturned tanker.
Cheshire Police have reduced the cordon around the scene to 400m from the original 1,800m.
Highways England patrolled the tailbacks for hours on Tuesday night, helping anyone who was in need of assistance.
Thousands of motorist who were caught in the tailbacks were also advised to turn off their air conditioning ventilation system and close all car windows.
The Liverpool to Runcorn train line through Helsby also suffered long delays as a result of the incident, causing long delays on services between Runcorn, Chester and Liverpool.
Major traffic issues remain and motorists have been advised to avoid this stretch of the M56.