Investigators met with Mexican authorities at the Chicago consulate this week and requested assistance as they seek to speak with other extended family members in Mexico.
Anabel Flores Salazar, a crime-beat reporter for a local newspapers, was dragged from her home in Orizaba, Veracruz by armed assailants on Monday.
The parents were originally from the Mexican state of Guanajuato and had lived in Chicago for about a decade.
Two children, two men and two women were found dead. They were originally from Guanajuato.
List of the top Mexican drug cartel captures or killings in recent years.
Gisela Mota had just sworn as mayor of Temixco on January 1.
Police and firefighters say hospitals treated at least 35 people from several states, Mexico and Canada. Six people remained hospitalized Wednesday, including two in critical condition.
Activists said armed guards from a shadowy company based in Mexico state pull migrants from trains.
A man and a woman suspected of taking part in the shooting attack died in a shootout with police hours later.
The burned remains of the mother and her children were found inside the simple wooden home.