At least 30 of the giant bolts that hold together the new, $6.4 billion eastern span of the Bay Bridge have snapped.

As a result, Caltrans is considering replacing all 288 of the bolts on the new bridge before it opens, The Chronicle has learned.

Caltrans insists the new span is safe and that plans to open it the day after Labor Day are still on track.

However, officials say it's too early to determine how long it will take to fix the problem - or the cost.

Toll Bridge Program Manager Tony Anziano said engineers are "pretty confident" the problem with the bolts is not a design issue or a construction problem but related to the quality of the steel bolts themselves.

"This isn't exotic - this isn't some wild issue," Anziano said.

Unlike the Chinese-built deck sections, the bolts - some as long as 17 feet - were produced in the United States.

"It appears to be a type of materials problem - the presence of hydrogen in the metal," he said. The hydrogen makes the metal brittle.

The problem was first detected on a large concrete foundation and column that supports the most eastern end of the new single tower, where eight fabricated steel pieces are anchored into a concrete cap and into the bridge deck with the giant steel bolts.

The bolts, also known as rods, range in length from 9 to 17 feet, and have a 2 1/2-inch diameter.

The rods were inserted in 2008, before the roadway decking was installed, making access to many of them difficult.

This month, according to Anziano, construction crews began tightening the nuts on both ends of 96 bolts - only to return days later to find that one-third had popped loose, damaging the bolts.

"We have extracted samples so we can have a clear understanding of what went on," Anziano said. "We don't have a cost, but we will have a solution."

Anziano downplayed the latest construction problem, saying, "I'd be very surprised if you didn't look at any large structural project that used fasteners and didn't have an issue like that.

"That's why you have inspections," he said.

The bridge, which has been under construction for more than a decade, has had a history of trouble and setbacks - most notably when microscopic cracks were found in the steel deck sections being fabricated in China.

That problem delayed key work on the bridge for months while new fabrication procedures were developed.

There were also questions about the integrity of the welds on the piers of the new skyway section, leading to further inspections before that work was cleared.

Plus, there was the accusation that an inspector who had worked on the bridge project had faked seismic inspection reports on another, unrelated project. That raised questions about whether he had taken similar shortcuts on concrete inspections on the new bridge.

Officials at the Metropolitan Transportation Commission, which is overseeing the project with Caltrans, will meet Wednesday for a full briefing on the problem.