Cause of mass pile-up of eight vehicles at Five Dock, Sydney was an out-of-control fuel tanker as police investigate whether mechanical failure was the cause

A horrific eight-vehicle crash that left six people requiring medical attention may have been caused by a mechanical failure in an out-of-control truck.

CCTV captured the Scania diesel tanker plowing through the intersection of Parramatta and Great Northern Roads in Five Dock, Sydney, during rush hour on Friday.

The truck mounted a curb before colliding with seven other vehicles stopped at traffic lights, leaving a trail of hoods and doors on the road.

Emergency services responded at 4.30pm and were assisted by a group of tradies who sprang into action, securing vehicles and removing the people inside.

Police are now investigating what could have caused the pile-up, which spread across three eastbound lanes of Parramatta Road and covered even more debris.

Six people from four cars suffered non-life-threatening injuries as a result of the crash in which a group of tradies pushed a car back onto the road to help the person in the car

One theory being considered by NSW Police is that a mechanical fault in the truck may have prevented it from stopping at the intersection.

“The truck drove through the intersection, mounting the curb before continuing eastbound, while a Holden Captiva struck a Nissan X-Trail stopped in the westbound lanes,” NSW Police said in a statement.

The truck plowed through the line of cars before the driver, 53-year-old Hamish Middleton, could pull into a nearby gas station.

The police seized the relatively undamaged truck at the scene and took it away for mechanical examination.

'He just drove straight through seven cars and kept going, it was horrific. I've never seen anything like this before,” a witness told 7News.

There was a car on each corner of the intersection, and one crash survivor, Maddi Brunton, said her car wasn't even hit by the truck itself.

“Everyone else got knocked out and then we got hit by the other cars,” she told 7News.

'[I’m] “I'm just glad we're okay, as long as my passenger is okay then I'm okay,” she later told 9News.

Bystanders and a group of tradies assisted in the recovery efforts, with the group of traders physically lifting a car back onto the road to help the person inside.

Paramedics treated six people from four cars who suffered non-life-threatening injuries before taking them to various area hospitals.

Police responded to reports of a serious collision at 4:30 p.m. and arrived to see the wreckage of a car on each corner of the intersection

The wreckage stretched across three lanes of one of Sydney's busiest roads and debris had flown onto another road, but miraculously no one was seriously injured.

Including the injured a 47-year-old woman driving a Mazda 3 and her 56-year-old passenger, a 33-year-old female driver of an MG, the 62-year-old male driver of a Holden Captiva, a 56-year-old male driver of a Toyota Corolla and his 57-year-old female passenger.

Four more women a 27-year-old VW Jetta driver, 54-year-old Hyundai driver, 23-year-old Mazda 6 driver and a 23-year-old Nissan X-trail driver were also affected by the crash, but were able to walk away unscathed.

A crime scene was set up near the intersection and inspected by police specialist officers from the metropolitan crash investigation unit before the wrecked cars were removed late on Friday evening.

Mr Middleton, from New Zealand, escaped without injury and returned a negative on-site breath test.

Witnesses described him as pale, shaking and in complete shock after he first left the cab of the truck, shouting for someone to call triple-0.

The police temporarily took Mr Middleton away to Burwood Police Station before releasing him shortly afterwards.

Mr. Middleton is an experienced truck driver and has been driving trucks for over 27 years.

His employer, APW, said it was cooperating with authorities in their investigation and would provide any support necessary to assist the process.

The truck driver, 53-year-old Hamish Middleton from New Zealand, has been driving trucks for 27 years (in an earlier photo)