Police have also revealed they are checking vehicles owned by a company linked to a deadly multi-vehicle smash in south-west Sydney.

Tuesday's crash, involving a truck and five cars on the Hume Highway near Campbelltown, killed the 57-year-old truck driver.

Fourteen others, including a month-old baby and two toddlers, were admitted to hospital.

Inspector Phil Brooks of the Traffic and Highway Patrol Command said yesterday the company that owned the truck was under scrutiny.

"We've had other trucks coming in from the company's fleet, only about six or seven at this stage, and we are finding some defects in those trucks and we're taking action as we find them," Insp Brooks said.

He said the crash came midway through a week-long joint operation with Roads and Maritime Services (RMS).

Operation Steel 5 has involved the inspection of 517 prime movers and trailers, and led to 185 defect notices being issued.

By 1pm yesterday three trucks had been grounded, with 27 major defects and 123 minor defects detected, and 32 formal warnings had been given.

NSW Police Traffic and Highway Patrol commander, Assistant Commissioner John Hartley, said the operation would continue throughout metropolitan Sydney until 2pm tomorrow.

"So far we have identified 344 mechanical faults; detected 57 breaches relating to improperly restrained loads; and conducted 363 random breath tests," he said.

"The operation is far from over.

"The NSW Police Force and RMS intend to track down and remove all trucks that do not comply with the state's road regulations." AAP