SAN FRANCISCO — Officials in charge of building a new eastern span of the San Francisco-Oakland Bay Bridge repeatedly questioned the work and quality control of companies involved in making long seismic safety bolts that broke while being tightened.
In March, a third of the 96 bolts failed, and transportation officials said it could take months to find the cause and fix the problem, meaning the scheduled Labor Day opening of the new $6.3 billion span could be in jeopardy.
Hundreds of pages of documents released to news media by the California Department of Transportation show that its inspectors found structural integrity issues with some of the bolts several years ago, before they were installed.
The documents were unclear about whether issues flagged by Caltrans’s own inspectors in 2007 and 2008 were remedied before the bolts were delivered and installed.
The inspectors noted that the bolts failed elongation tests for structural integrity and said they were concerned about the quality of work by a company that galvanized the bolts to prevent corrosion.
Inspectors said bolts made by Painesville, Ohio-based Dyson Corp. had failed to meet certain standards during testing on three occasions.
Andrew Gordon, a Caltrans spokesman, said the agency would not comment during an ongoing investigation into why the bolts failed. Dyson Corp. also has said it will not comment during the probe into the bolt failures.
The bridge’s main contractor, American Bridge Fluor, an Oakland-based joint venture, did not return a call seeking comment.
Metallurgists said the documents contained no clear explanation about why the bolts cracked, but they suggested that the cause was most likely a confluence of missteps during manufacture and installation.
‘‘This is most likely a perfect storm situation,’’ said David Xu, a mechanical engineer and metallurgist at Berkeley Engineering and Research Inc. ‘‘A lot of these factors alone might not have caused this issue, but together most likely could have pushed it over the edge.’’