But the drama continues as the trucking company involved in the accident - which saw 60 metres of asbestos tiles ripped from the tunnel ceiling - refutes ACT government claims it was hauling the excavator illegally.

There have been no penalties issued over the incident, with WorkSafe ACT commissioner Mark McCabe saying the results of an investigation could be weeks or even months away.

Roads Minister Mick Gentleman said on Wednesday that the truck did not have the required permit for its load but a spokesman for Charman Earthmoving and Heavy Haulage, John Kananghinis, said on Thursday the haulage was planned to be undertaken "within normal operational conditions and regulations" with "no requirement for special permits".

"What we can say clearly is these loads when operated correctly do not require a special permit. The final details need to be fully established with the investigating authorities."

He said the company was reviewing its training procedures, "irrespective of whether any revised action is required by regulation or not".

The company would not speculate on the costs involved with the operation but apologised for the inconvenience caused.

"They appear to have an exemplary safety record, that's not to say that incidents can't occur and it has occurred and the company regrets and apologises for the inconvenience," Mr Kananghinis said.

"[Costs are] a matter that the company, their insurers and the authorities will work through once they've cleaned up the scene and identified exactly what's happened. Then they'll be able to identify what level of responsibility lay and what happens next in terms."

The family owned company won a Safe Work ACT Award five years ago which recognises high standards of occupational health and safety.

Once the truck emerged from the tunnel at about 2.30pm, it underwent a WorkSafe ACT check to ensure it was in a condition to take the excavator across town and have its prohibition order removed.

The excavator still has a prohibition notice on it and so is not permitted to be used until cleared by WorkSafe, ACT Work Safety Commissioner Mark McCabe said.

The truck and excavator will be housed at the company's compound while the WorkSafe investigation continues to determine if anyone was at fault.

"The penalties can be quite significant, penalties under work health and safety legislation go as high as three million dollars, [it] probably wouldn't be that high for an incident like this, but that's jumping ahead.

"We've got to complete our investigation, find out who was at fault, if anyone."

Mr McCabe described the debacle as an "expensive exercise".

"[It's] a very expensive exercise for what is in some ways a very simple accident but it has big ramifications. It just shows you how dependant we are on our major arterial roads. If one gets blocked it can have a good impact."

ACT roads director Tony Gill agreed the operation was of "significant scale" with his staff and contractors engaged around the clock.

He said the priority has been to get the tunnel cleared but costs would be examined in the near future.

"The ACT will look at what costs it can recover through its various insurances and the insurances of the parties involved," he said.

There are plans to replace the tunnel's ceiling tiles at a later date and outside of peak times.

Thursday morning was a commuter nightmare after multiple accidents compounded the delays caused by the closure of Acton Tunnel.

An eight-car pile-up clogged traffic at the intersection of the Tuggeranong Parkway and Hindmarsh Drive shortly after 9am.

Minutes later, a car fire flared up at the Glenloch Interchange. An ACTION bus also blew a turbocharger near the National Zoo and Aquarium.

The traffic troubles continued an hour later with a two-car crash on the parkway's southbound off-ramp onto Hindmarsh Drive at Lyons.