The existence of the investigation and the problematic bolts was first reported by WNBC-TV.

NBC reported that some of the allegations emerged through a whistle-blower complaint filed by a former safety inspector; the complaint included a conversation with an ironworker foreman about the broken bolts. A partial transcript of that conversation was included in a PowerPoint presentation made by a law firm for the whistle-blower, which was obtained by The New York Times.

“That’s a spot that doesn’t break,” the foreman says of the part of the bolt that broke, according to the transcript, the foreman describes the fracture as “a major defect that does not normally occur” and, if discovered, “would probably shut the whole job down.”

Contractors faced a deadline in 2018, and for each day it exceeded the deadline, it would owe money to the state in the neighborhood of $100,000 a day.

The presentation suggests that the bolts failed because of so-called hydrogen embrittlement — the same problem that plagued the San Francisco Bay Bridge in California, and which had to be repaired at great expense.

State officials in New York began testing the bolts — there are as many as one million used in the bridge — as early as February 2016, before it was aware of the investigation, a state official said. An outside engineering firm, Alta Vista, completed a study in late 2017; the report, obtained by The Times, concluded there was “compelling evidence” that hydrogen embrittlement “is not a cause of the observed bolt failures.”