The charred wreckage of the petrol tanker lies on its side on Mona Vale Road. Photo: Kate Geraghty
Police have issued 26 defect notices to the trucking company involved in Tuesday's horrific fuel tanker crash on Sydney's northern beaches.
Emergency crews have removed the charred remains of a tanker from the crash scene on Mona Vale Road, where it ploughed into a power pole and four cars on Tuesday before erupting in a fireball.
Fatal car crash in Mona Vale
The road is closed as the truck fire rages out of control. Photo: Tim Pascoe
Two men died in the blaze and six others were taken to hospital.
A police spokeswoman said 12 heavy vehicles from the company had been checked by 5pm, and that officers had issued 26 "major defects".
She said the defects were for a range of offences, including brakes, wheels and suspension faults.
RMS and police said on Wednesday they are inspecting more than 80 fleet vehicles from Cootes Transport, which have been directed to checking stations in Sydney and Newcastle.
RMS has previously said that the inspections "will inform a decision on whether or not other vehicles in the Cootes' fleet will be subject to roadworthiness inspections".
In a statement, Cootes said it would "co-operate fully" with investigations into the incident.
Earlier, Assistant Commissioner John Hartley said it was still unclear what caused the truck to lose control, overturn, then explode into flames.
"We're investigating why the truck was out of control what the lead up to the crash was, whether that was driver error or a mechanical failure," Assistant Commissioner Hartley said.
"Obviously gear failure, brake failure, all those sorts of things could stop a truck from pulling up."
He said the investigation would take "many weeks", and that police were still waiting on the return of blood and urine tests from the driver.
Police believe the truck appeared to have lost control, hit a power pole and four other cars before turning on its side and dousing the road in fuel.
It's likely the huge explosion that followed was caused by a spark from the friction of the crash.
The two men killed in the incident, a 73-year-old from Turramurra and a 71-year-old Western Australian, are believed to be the driver and passenger of a Subaru.
Other passengers, two women aged 67 and 72, are both in a stable condition, while a 69-year-old Warriewood man is in a serious but stable condition.
A 75-year-old woman has also been discharged.
The truck driver, a 47-year-old from Wagga Wagga, is in a stable condition at Royal North Shore Hospital.
About 300 litres of petrol were spilled onto the road in the process of getting the truck upright, and an unknown amount ran into local drains.
The clean-up is expected be completed within days.