The truck which brought Sydney's CBD to a grinding halt in a tunnel crash was not safe to be on the road, police say.

Officials have spent the day inspecting all 21 trucks owned by The Good Soil company after one of its tip trucks became struck in the Eastern Distributor near Moore Park early yesterday.

Its back tray lifted while it was entering the tunnel, disrupting traffic for seven hours.

The Commander of the Traffic and Highway Patrol Command, Superintendent Stuart Smith says the fleet inspection has found seven defects, including in the truck involved in the tunnel crash.

"That vehicle is not in a roadworthy condition and has significant brake defects," Superintendent Smith said.

Despite that police say it is not yet clear if the crash was caused by driver error or mechanical problems.

The truck's hydraulics have been examined and the company's maintenance records have been seized.

It took more than an hour to free the truck driver after yesterday's crash.

He was taken to hospital with minor injuries.

"It's always disappointing. The service history of trucks and the service programs that trucking companies practice are complex and expensive, but there's an expectation that needs to be met, that these things are safe when they hit the road," Superintendent Smith.

"Obviously yesterday's incident closes the road system and seriously disadvantages business in NSW."

The Good Soil company issued a statement this afternoon.

"I want to extend our deep and sincere apology to the people of Sydney for the inconvenience and frustration yesterday's accident caused," it said.

"We are a family business and have been operating without incident since the company started 14 years ago.

"We are co-operating fully with the police and the RMS in their investigations.

"We will do everything we can to make sure this cannot happen again."

Second truck tunnel crash in Sydney in two months

A similar crash damaged Sydney's M5 East tunnel in November, causing significant traffic delays.

A tip truck hit the tunnel's roof when it also entered with its tray raised, bringing down overhead pipes and lighting.

The State Roads Minister Duncan Gay says motorists should not have to suffer because of such of accidents.

"Once I got over my initial anger, first of all the odds of having one truck with the tipping body come up in a tunnel was just unbelievable," Mr Gay said.

"To have a second one within a month is equal. I was angry. I suspect the people of Sydney was just as furious as I was at the stupidity of these two situations."

Southbound lanes of the tunnel will be closed for the next two nights to allow for repairs.

The road will be shut tonight between 11pm and 5am tomorrow, then tomorrow night between midnight and 5am.

Police have reminded truck drivers who ignore height restrictions they can be fined up to $5,500 in court, while truck companies who repeatedly transgress can be fined up to $55,000.