BOSTON (AP) – A Big Dig ramp, closed amid safety concerns in the wake of the deadly collapse of a nearby tunnel ceiling, reopened shortly after midnight Tuesday.

A hotel van and about half a dozen cars were the first vehicles through the eastbound ramp that funnels traffic toward the Ted Williams Tunnel and Boston’s Logan International Airport. It is a key to easing traffic congestion originating south of the city.

The ramp was closed shortly after an accident July 10 that killed a 39-year-old woman as she and her husband drove through a connector tunnel and their car was crushed by 12 tons of falling ceiling panels.

“The portion that’s just being opened, Ramp A, is safe,” Gov. Mitt Romney declared at a Statehouse news conference on Tuesday afternoon.

He cautioned, however, that plenty of work remained in other tunnels closed since the accident and problems continue to come up as engineers review the safety of the tunnel network.

“Is there going to be more work done? Absolutely,” Romney said. “But I feel very confident when I walk through (Ramp A). I’ll feel more confident when I’m driving through it. It’s a lot safer than a lot of other things we do. And I feel that Ramp A is safe.”

Ramp A represents only about 10 percent of the total area of the Big Dig tunnels and ramps that have been shut down since 39-year-old Milena Del Valle was killed.

General traffic will now enter the Ted Williams Tunnel eastbound to the airport from a surface bypass road in South Boston. The eastbound tunnel has been open only to buses, while other traffic has been diverted to older airport tunnels that cannot accommodate some trucks.

“This makes a huge difference,” Romney said. “Both directions, eastbound and westbound, will now be able to have cargo trucks going in both directions, automobiles can go both directions.”

The Federal Highway Administration and Office of Inspector General at the U.S. Department of Transportation said the decision to reopen was the result of a thorough inspection of tunnel repairs and “the state’s implementation of an aggressive plan to monitor the reopened areas.”

Since the accident, authorities have focused on the bolt-and-epoxy system that failed to hold suspended ceiling panels in place where Del Valle was killed. Inspections have revealed slippage in dozens of other tunnel locations, and workers have been reinforcing potentially weak connections.

Romney said Tuesday that inspectors over the weekend also discovered that brackets used to connect the panels to the ceiling weren’t big enough, and workers had to replace 23 brackets.

The governor also criticized Big Dig project manager Bechtel/Parsons Brinckerhoff for not having noticed earlier that the brackets being used by contractors was not sufficient.

“The basic system had an area of flaw that hadn’t been identified before,” he said. “It’s hard to understand how it is that the engineering firm responsible for the integrity and quality assurance of the entire project would not have done a calculation of these connector brackets and determine that they did not meet the specifications that had been set for this project.”

Romney said it raises “very serious concerns about the oversight by these engineering firms of this project.”

Bechtel/Parsons Brinckerhoff stood by its work.

“We firmly believe the projects processes for engineering, construction, and quality assurance were appropriate and robust,” the company said in a statement. “We are proud to have been a part of one of the largest, most complex, and technically challenging projects ever undertaken in an urban setting and which already has transformed Boston into a more livable, attractive, and economically vibrant city.”

Other tunnel sections closed after the accident could take months to inspect and reopen, Romney said.

The Big Dig highway project buried the old Central Artery that used to slice through the city, creating a series of tunnels to bring traffic underground. Although it’s been billed an engineering marvel, the most expensive highway project in U.S. history also has also been plagued by leaks, falling debris, delays and other problems linked to faulty construction.

The initial price tag for the project was $2.6 billion and it was supposed to be completed in seven years. Instead, it took nearly 15 years and repeated cost overruns drove up the price to $14.6 billion.

After the July 10 accident, Romney seized control over inspections, promising a “stem to stern” safety audit. He also forced out the head of the Massachusetts Turnpike Authority, which oversees the Big Dig.

State and federal criminal investigations are under way to determine if construction failures are the result of criminal negligence.

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AP reporters Steve LeBlanc and Ken Maguire contributed to this report.

AP-ES-08-09-06 0012EDT