Chicago police arrested two suspects - a man and a woman - Thursday in the brutal slayings of six family members whose bodies were found in a house in February, according to a police spokesman.
Police spokesman Anthony Guglielmi said the man has a family connection with the victims, and that authorities are planning to charge both with first-degree murder.
"The arrests were made without incident in Chicago after several search warrants were executed," Guglielmi said.
Authorities found the bodies of four adults and two children, ages 10 and 13, Feb. 4. Five of the victims were stabbed to death; the sixth died of multiple gunshot wounds.
Chicago Police Superintendent Eddie Johnson was expected to outline the development in the case at a news conference Thursday evening. He declined to answer questions at an unrelated news conference earlier in the day.
Mexicans have followed news of the killings closely and Mexico's consulate took a special interest in the case.
The father of the two dead children, Manuel Armando Cruz, was granted a U.S. humanitarian visa to fly from his home in Morelos, Mexico, to attend funeral services at St. Gall Catholic Church in Chicago.
Both the U.S. and Mexican governments helped with paperwork to send all six bodies to Mexico for burial.
Police previously said there were no signs of forced entry to the residence in the Gage Park neighborhood, the doors were locked, the home didn't appear ransacked and the victims weren't bound.
The extent of the grisly killings was made clear in autopsy reports. Maria Herminia Martinez, 32, had four bullet wounds to her head and gunshots to each of her hands, and Noe Martinez Sr., 62, had 42 knife wounds all over his body, the Cook County medical examiner's reports said.
The autopsy reports said two small-caliber bullets and a fragment were recovered from Herminia Martinez's body.
The documents also said that her 13-year-old son, Leonardo Cruz, was stabbed in his head, cheek, neck and shoulder. His body was found near a living room fireplace with a textbook, ruler and pencil nearby.
Martinez Sr. was stabbed in his left hand, neck, chest, groin and left leg. He was found wearing an unzipped black winter jacket with a pocketknife nearby in a front hallway.
Rosaura Martinez, 58, was stabbed five times in the abdomen, had a cut across her face and arteries in her neck were slashed. She was wearing pajamas and her hands were badly cut and her left wrist dislocated.
Alexis Cruz, 10, was found stabbed repeatedly and left on an area rug not far from a book bag filled with drawings. He suffered three wounds to his heart and wounds to his lung and liver.
The body of Noe Martinez Jr., 32, was marked with knife wounds and he was found battered on his head.