(CNN) Democratic gubernatorial nominee Andrew Gillum received a ticket to the Broadway show "Hamilton" from a group that included an undercover FBI agent, according to text and email records released on Tuesday under subpoena by the lawyer for a former Florida lobbyist.

The revelation is the latest development regarding a federal investigation into public corruption in Tallahassee, Florida, where Gillum has been mayor since 2014.The records, which were subpoenaed by the state ethics commissions last week according to the Tampa Bay Times, cast doubt on the explanation from Gillum's campaign that the mayor received the ticket from his brother Marcus.

The FBI probe centers on whether developers successfully influenced city projects. At one point in the probe, an undercover agent successfully infiltrated Gillum's inner circle. No one has been charged with any wrongdoing.

Gillum has repeatedly said the FBI told him he is not a focus of the investigation. But his attendance at a Broadway show with lobbyist and longtime friend Adam Corey, along with his brother and the federal agent, who went by Mike Miller, has been used by political opponents to suggest Gillum is potentially under more direct scrutiny.

At issue is a 2016 trip to New York, where the group saw the hit musical "Hamilton." Gillum's campaign has said his brother was the source for his ticket. But within the nearly 150 pages of records provided on Tuesday by Corey to ethics officials, text messages between Gillum and Corey present a murkier picture.

Read More