We're now learning that federally charged Department of Public Works Director Mohammed Nuru may have been trying to watch the backs of "bigger fish" in City Hall when he placed a phone call following his initial arrest by the FBI.

We knew when the first reports came out last week that Nuru allegedly violated an agreement he had made with federal prosecutors last month, leading to an additional charge against him: lying to investigators. Now, via the Chronicle's Phil Matier, we learn the details of that charge — Matier discovers that behind the charge was a call Nuru allegedly made to his boss at City Hall, City Administrator Naomi Kelly, to inform her (and by extension, the mayor) of the FBI probe into his department.

Matier talks to former federal prosecutor Tony Brass, who suggests that the reason the feds would have made some sort of cooperation agreement with Nuru in the first place is that they likely had a bigger target in mind, and they were looking to "flip" Nuru in order to get more information. Who would that be?

Abraham Simmons, a spokesperson for the U.S. attorney’s office, tells the Chronicle, "The record doesn’t specify the sort of cooperation in which Mr. Nuru might have agreed to participate."

The situation is reminiscent of the lengthy federal probe into the political web connected to convicted Chinese mafia figure Raymond "Shrimp Boy" Chow. During that mess five years ago, San Francisco school board member Keith Jackson was caught on a wiretap accepting money to set up a meeting between a fictional out-of-town developer and Mayor Ed Lee. And in an August 2015 federal court filing by the defense in Chow's trial, both Mayor Ed Lee and then Supervisor London Breed's names were mentioned as being implicated in the prosecution's discovery materials regarding "pay to play" schemes in the city.

Both parties vehemently denied the report, and no charges ever arrived against Lee or Breed. Breed said at the time, "The only thing I’ve learned from this sad episode is that you should be very skeptical of what you read in the news, especially when it comes from an accused felon looking for anyone but himself to blame."

But the most damning quote came from Human Rights Commission staffer Zula Jones, whom the feds allegedly had on tape saying that Ed Lee "learned from the best" (former Mayor Willie Brown) when it came to pay-to-play schemes. "You got to pay to play here," she was quoted as saying. "We got it. We know this. We are the best at this game, uh, better than New York. We do it a little more sophisticated than New Yorkers. We do it without the mafia."

So how wide and how deep will all this end up going? There's ongoing investigation, clearly, and the arrest of Nuru and alleged co-conspirator Nick Bovis may just be the tip of the iceberg.

Former FBI agent Rick Smith puts it bluntly to the Chronicle: "There is a culture of corruption here, and the U.S. attorney is going after that culture."

In other new news, Bovis and Nuru were apparently working to bring a casino, via a Chinese investor, to an undisclosed property in Northern California — a potential cash cow that Matier surmises might have been the pair's ultimate goal, beyond the comparative nickels and dimes of the restaurant contracts for Bovis.

Also, the Chronicle reports that a pair of Detroit businessmen, under threat of federal investigation themselves, acted as informants for federal investigators in the SF investigation. The two men, Samir Mashni and Noureddine “Dean” Hachem, began recording calls and meetings that they had with Bovis and Nuru back in January 2018. One of the men, according to the federal complaint, appears to have worked with Bovis on his effort to open a location of his Spinnerie roast chicken restaurant at SFO. Mashni and Hachem own a company that operates airport concession outposts, including a coffee concession at SFO.

Mission Local reports that federal agents visited the Department of Building Inspection today, possibly looking for files pertaining to 555 Fulton — the building that figures in the alleged "scheme" in which Nuru received a luxury vacation in China at the hands of a Chinese developer.

Both Bovis and Nuru will appear in federal court Thursday for bond hearing.

Previously: City Attorney Vows Thorough, Independent Investigation Of City Contracts Linked To Nuru