Mexico City's mayor says investigators will travel to the Gulf coast state of Veracruz to question its governor about the July 31 killing of a photojournalist.

Veracruz Gov. Javier Duarte tells local media he has no knowledge of the incident, which happened in a Mexico City apartment where four women were also slain.

Photographer Ruben Espinosa had fled Veracruz recently, saying he feared for his safety due to his work covering protests.

Thirteen journalists have been killed in the state since Duarte took office in 2010.

One suspect has been arrested. The crime showed some signs of violent robbery.

But Mayor Miguel Angel Mancera says all lines of investigation are open including possible political motives.

Mancera said Monday that an investigative team would go to Veracruz the next day.