(CNN) Newly discovered nude cell phone photos may be evidence Nashville's mayor and her former security chief were having an affair while he was being paid to be her bodyguard, authorities say in court documents disclosed Thursday.

In filing affidavits for search warrants, the Tennessee Bureau of Investigation says Rob Forrest used a work phone to take two photos while on duty. Investigators say evidence points to the possibility that crimes -- official misconduct and theft of property -- occurred.

"(Probable cause exists to) show that on May 15, 2017 and on October 18, 2017, he used this phone to photograph a nude or partially nude female," the documents say. "It will also show that Rob Forrest's timecards report that he was working while these photographs were taken."

The TBI "believes probable cause exists to show that Rob Forrest was indeed not working at the time (two photos) were taken but was rather participating in the affair with Megan Barry at these times," the document adds.

TBI investigators say they looked at Forrest's phone and his emails after Barry admitted publicly to the affair. Two of his emails each contained one photo that showed a partially nude or fully naked woman, court documents say. The documents do not say the woman is the mayor.

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