A newspaper reported Sunday that it has found records of an apparent defect in the construction of the new San Francisco-Oakland Bay Bridge.

Records provided by Caltrans last fall show that a builder failed to report that a 19-foot section of concrete in the foundation of the span's signature tower had not hardened before tests were conducted, according to The Sacramento Bee .

By failing to disclose the matter, the builder prevented further examination or repair of the concrete, the newspaper said.

Kiewit-FCI-Manson, an Oakland-based joint venture, built the foundation as part of a $177 million contract. It did not provide the 2007 test results until after a Bee investigation in November showed that a Caltrans employee skipped required test preparation for separate checks of the same foundation and fabricated results on other Caltrans projects, the newspaper said.

The newspaper said experts who reviewed concrete and engineering records for The Bee questioned the ability of the main tower foundation to resist an extreme earthquake, which was the reason for building the new bridge.

Caltrans says it believes the concrete has hardened and that the bridge is sound and can withstand any anticipated earthquake.

Besides the concrete in question, the Bee's examination also found other problems with the piles, as well as with test data.

During its review of Caltrans records, The Bee said it also found that two of the 13 piles that rise out of the Bay to hold up the main tower were not tested properly.

Among the more than 20 errors found in test reports, according to The Bee, were errors indicating what piles were tested, the test dates and pile measurements.

Olson Engineering, a Colorado-based firm, which conducted sonic tests of the piles, detected the problem concrete in 2007, referring to it as "a batch of concrete that has not fully set at the time of testing" or "a very poor area of concrete."

The company suggested new sonic tests, but no new tests were conducted, according to Caltrans.

When The Bee asked Olson president, Larry Olson about the tests, he referred questions to Kiewit Corp., which referred questions to Caltrans.

In an email to The Bee, Caltrans spokeswoman Tamie McGowen said "substantial evidence" indicated that the abnormal concrete in one of the piles, referred to as Pile 3, eventually hardened properly.

"We are confident in the structural integrity of the main tower foundation and that the bridge will perform as designed to handle an extreme earthquake," McGowen wrote.

Caltrans plans to open the $6.5 billion structure by Labor Day 2013 to serve an estimated 100 million drivers annually.