Three were people taken to hospital and another was assessed at the scene by paramedics after the collision close to Seaham and Murton on the southbound side of the carriageway at around 8pm yesterday, Thursday, March 4.
Diversions were put in place for motorists as the emergency services closed the road while they worked to deal with the incident, which Highways England classed as a “serious collision”.
Its officers also attended the crash site to support police, medics and help clear the carriageway.
It confirmed the route reopened to traffic at around 4am today, having been closed off from the A182 at Murton and the A1086 at Easington.
The North East Ambulance Service confirmed it took three people to hospital and had called in help from the Great North Air Ambulance.
In the aftermath of the crash, a spokesperson said: “We have attended a road traffic collision on the A19 southbound in Seaham this evening.
"We dispatched eight resources in total, including four crews from our Hazardous Area Response Team, a specialist paramedic and two ambulance crews, as well as requesting support from Great North Air Ambulance Service.
"We assessed four patients on scene and have transported one patient to James Cook Hospital and two patients to Sunderland Royal Hospital.”
Anyone who can help police with inquiries into the collision can contact Durham Constabulary on 101.