A trucking company involved in a highway crash which killed two young brothers has been found to have several faults in its fleet, including brake defects and tired drivers.
The two boys, aged nine and 12, died at the scene on the Newell Highway, north of Dubbo, after the Queensland family's 4WD collided with a Redstar Transport truck last Saturday.
A third brother, aged four, suffered internal injuries and was taken to Sydney's Westmead Children's Hospital in a serious condition, while the parents escaped with minor injuries.
The driver of the truck, aged in his early 50s, suffered back injuries.
Police raids on Friday morning uncovered several faults in the Redstart fleet at their depots in the western Sydney suburb of Yennora and also at Dubbo.
Police assistant commissioner Michael Corboy said authorities audited the entire Redstar fleet, consisting of about 160 prime-movers and up to 600 trailers, across all states.
After the first 50 checks, several issues including major load problems, defects with brakes and suspension and logbook falsification were uncovered.
In total, 22 defect notices were issued, including 15 for major defects, 20 infringements were issued for a range of offences, one driver was found not carrying a licence and 29 drivers were tested for drugs.
"During the operation we have found there to be trucks with unsecure loads and tired drivers," Mr Corby said in a statement.
"We make no apologies for detecting and prosecuting these types of offences which are putting lives at risk."
Roads and Maritime director of compliance Roger Weeks said in the statement it was "disappointing" the operation revealed trucks with unsecure loads and seven with major defects.
Action will be taken against the company once the audit is completed.
The investigation into Saturday's shocking crash will look at whether the truck driver was fatigued.
Crash investigators are also looking at whether the collision was a side-swipe, the assistant commissioner said.
"The father of the family did everything he could to avoid the accident," Mr Corboy said.
The crash was so violent the accident site stretched more than 500 metres along the highway, with footage showing the white 4WD ripped in two on the side of the road.
A Redstar spokesman said the company is cooperating fully with authorities.
He said Redstar is not anticipating any significant issues from the audit.