Mexico City (CNN) -- A judge has issued arrest warrants for 20 people wanted in connection with the kidnapping and killing of the son of poet Javier Sicilia, Mexico's Attorney General's Office said Sunday.
The warrants were the latest advance in a high-profile case which has captivated the Mexican public and drawn attention from the country's top officials.
"These subjects are suspected in kidnapping, homicide and other crimes against Juan Francisco Sicilia Ortega" and six others, the Attorney General's Office said in a statement.
Sicilia has become one of the most outspoken opponents of Mexico's drug war and widespread drug-related violence since his son's slaying in March. The poet has led large demonstrations in Mexico City and the violence-plagued Ciudad Juarez. He has also vocally criticized officials' handling of the case.
In a meeting with Mexican President Felipe Calderon last month, he asked for a moment of silence for the victims of what he called "an atrocious and senseless war."
Police found the lifeless body of Sicilia's 24-year-old son and six others crammed inside a car in the central Mexican town of Cuernavaca on March 28. Masking tape was wrapped around their heads, faces, wrists and ankles.
Authorities believe all seven victims suffocated, and they have said members of Mexico's Pacifico Sur cartel are suspects. At least several suspects have been arrested.
Attorney Julio Hernandez, who represents Sicilia, said Sunday that police still had not detained one person directly involved in the case, state media reported. Authorities are offering a reward of 300 million pesos ($25.5 million) for his capture.