HAYWARD — The city of Hayward investigated an allegation that police Chief Diane Stuart showed favoritism toward a contractor who later became her husband, this newspaper has learned.

It is unknown if the allegation is related to the city’s decision Monday to place Stuart on administrative leave while looking into a personnel issue.

Former City Manager Fran David, who retired July 31, confirmed she received and investigated allegations in an anonymous letter that Chief Stuart — then known as Diane Urban — “traded favors” with Clark D. Stuart II, who has worked as a contractor for the city over the past several years. The two recently were married, and social media posts indicate their personal relationship dates back at least two years.

The undated letter was apparently sent before the chief and Stuart were married. It indicates it was mailed to this newspaper, Mayor Barbara Halliday, the chief and Clark Stuart, among others.

Halliday said she vaguely recalled receiving the letter, but referred questions about it to current City Manager Kelly McAdoo. McAdoo did not respond immediately to a public request about the letter or Clark Stuart’s involvement with the police department.

David did speak briefly about the letter. She confirmed that she received it and investigated the matter but declined to elaborate further, citing the city’s ongoing investigation.

“I don’t want to jeopardize the investigation that the city is doing, and I don’t know if any, all or part of (the letter) is going to be a part of that — I just don’t want to misrepresent anything at this point,” David said.

Clark Stuart’s relationship with the city dates back to at least December 2011, when he was helping the Hayward Police Department “investigate violations of and enforce laws regarding human trafficking,” according to archived city records.

At that time, city agreements show that Clark Stuart’s company, Global Trident II, was given a one-year access to the Hayward Police Department’s confidential, proprietary database that stores information about sexual exploitation offenses.

The city also used a 2002 Ford Focus provided by Global Trident that was “specifically equipped with resources for conducting surveillance and other law enforcement activities,” according to a January 2012 agreement signed by David and then-Chief Urban.

The car was to be used jointly by Global Trident employees and Hayward police officers as a part of “ongoing investigations and enforcement of laws prohibiting human trafficking, prostitution and other quality of life offenses,” the signed accord read.

Clark Stuart was hired in 2014 to train senior staff “in critical areas such as customer service, communications, and professional development.” The agreement, which was reached before the chief and Clark Stuart were married, was not to exceed $75,000 for the two-year term. The contract was with the city manager’s office and was approved by the City Council.

Stuart recently taught a three-day class titled “effective executive communication,” which was hosted by the Hayward Police Department, according to Ralph Brown, a spokesman for the state’s Commission on Peace Officer Standards and Trainings. To teach the class, Stuart was first approved by POST, Brown said.

Numerous Bay Area police agencies have sent officers to Stuart’s classes. It’s common practice for agencies to send officers to trainings hosted by other agencies to offset costs.

Stuart, known as Diane Urban until her marriage to Stuart, a retired U.S. Navy officer, was appointed as the first woman to lead Hayward’s police department in August 2011, according to her bio on the city’s website. She began her law enforcement career in 1986 with the San Jose Police Department, climbing to the rank of assistant chief, at the time the highest-ranking female police officer in San Jose history.