The attorney for the man whose wife had an affair with Missouri Gov. Eric Greitens says a grand jury has convened in the case.

Attorney Al Watkins says a subpoena issued Monday calls for his client to testify before a grand jury in St. Louis. A spokeswoman for the city circuit attorney's office declined comment.

Greitens' attorney, Jim Bennett, says neither he nor Greitens has been contacted by law enforcement seeking information on the governor.

The Republican admitted in January to an affair with his St. Louis hairdresser in 2015. The woman's ex-husband secretly recorded a conversation with her in which she claimed that Greitens took a compromising photo of her as potential blackmail if she spoke about the affair.

Greitens has denied threatening blackmail.