More detours. More delays. More frustration.

Commuters got their first glimpse Monday of what to expect for at least the next couple of months as investigators and construction crews work on identifying and repairing problems in the tunnels of the city's Big Dig highway system.

Another tunnel ramp was shut down on Sunday because of what Gov. Mitt Romney called a "systemic failure," nearly a week after the collapse of 12 tons of cement ceiling panels in another section of tunnel that crushed a car carrying Milena Del Valle, 38.

The governor said testing on bolts used to secure the heavy concrete panels in the tunnel, which connects Interstate 90 west to Interstate 93, revealed dozens of potential problems.

"It looks like the problem is far more substantial than just an anomaly — that it is a systemic failure in the fastening system," Romney said. "For the entire system to be repaired and safe is probably going to take at least a couple of months, and perhaps longer."

Since Del Valle's death July 10, motorists had been using the ramp closed Sunday as a detour around the accident scene. But recent testing showed problems with 40 bolts that hold up the ceiling panels there, up from an initial 20, Romney said.

Traffic stacked up early Monday morning, complicated by at least two crashes in the areas of the tunnel shutdowns. State police said it was difficult to know what to blame on the latest ramp closure.

"It's sort of hard to attribute what's getting backed up from what here," Lt. Eric Anderson said.

The tunnel ramp closed Sunday had been previously identified by inspection teams as a potential trouble spot, said Jon Carlisle, a spokesman for the state Highway Department.

"We're putting additional connections between the roof and the ceiling panels," Carlisle said, adding that the specific number of repair spots was unclear. "We're still working on the engineering."

Romney said Sunday's closure was not called for because of any imminent danger. "We're just not willing to risk people's lives," he said.

Twelve tons of concrete ceiling panels crushed the passenger side of the car being driven by Del Valle's husband, Angel Del Valle, as they headed to Logan International Airport. Angel Del Valle escaped with minor injuries by squeezing through the car window.

Connector tunnels in both directions have been closed since.

State and federal investigators have focused on bolts used to hold the drop-ceiling system in place. Each of the concrete slabs suspended above the roadway weighs three tons.

Investigators are focusing on the bolts and the epoxy glue used to secure them.

Romney said Sunday that many of the bolts where epoxy was used would need to be replaced or better secured, and outlined three plans for the remediation, including an anchor bolt system, a steel-on-steel connection, and a cable system. He said removing the heavy panels isn't an option because they are "an integral part of the ventilation system."

Romney also identified three jet fans in the tunnel where Del Valle was killed that raised red flags.

"They showed signs of movement as well, therefore these jet fans are also going to have to be shored up," Romney said.

The majority of the bolt systems have now undergone pressure tests, Romney said. Pull tests are pending on bolts in the Ted Williams Tunnel, which remains open. Romney said the ceiling panels in the Ted Williams Tunnel are lighter — about 800 pounds each — and don't show signs of slippage.

The $14.6 billion Big Dig buried the old elevated Central Artery that used to slice through the city, replacing it with a series of tunnels. Although it's been considered an engineering marvel, the most expensive highway project in U.S. history also has also been plagued by leaks, falling debris, cost overruns, delays and problems linked to faulty construction.