SEATTLE — State transportation officials gave Seattle Tunnel Partners the OK on Tuesday to resume excavation on a pit being dug to reach and repair Bertha, the broken tunneling machine.

But officials still don’t know whether the recently discovered ground settlement was caused by all the water being drained from under the pit, according to Alaskan Way Viaduct Replacement project spokeswoman Laura Newborn. Workers have been “de-watering” to reduce pressure from underneath and on the sides of the hole.

Digging was stopped last week after monitoring systems detected 1 inch to 1.4 inch of ground settlement near the pit — under a section of the Highway 99 viaduct and buildings in historic Pioneer Square. No significant sinking has occurred since Dec. 5 so they said the digging can resume, she said.

Gov. Jay Inslee, speaking after a transportation press conference in Medina, said he was confident that the viaduct is safe, adding, “I drive my grandkids over it without any concern right now.”

“That is not to say we are not disappointed by this event,” Inslee said of the unexpected ground settlement. “This is something that is concerning. That’s why we’re paying so much attention to it.”

He also blamed the contractor — Seattle Tunnel Partners — for the state’s inability to say when the tunnel will open to traffic.

“We need to be very demanding on the contractor to make sure they give us information so that we can fully evaluate the repair project,” he said. “We need to be insistent that the contractor preform their contact, which is to give the people in the state of Washington a completed tunnel. They’re under a legal obligation to do that. We’re going to insist that they do that every single day.”

The $2 billion tunnel was the choice to replace the viaduct after it was damaged in the 2001 earthquake. Bertha, a state-of-the-art tunneling machine, stopped work on the 2-mile tunnel last December after about 1,000 feet and repairs are needed before drilling can resume. The access pit is about 84 feet deep and they’re trying to make it 120 feet so they can pull Bertha out and start the repairs.

“We will continue to conduct frequent surveys and analysis, including determining the cause of the observed settlement, and provide updates to the public,” Newborn said.