Authorities have no suspects and a motive remains elusive one week after six family members were found dead in their Chicago home, police said Thursday, with investigators now focusing on video evidence, the weapons used and interviews with relatives and acquaintances to try to glean clues about why the family was targeted.

The wounds indicate that three knives or knife-like weapons were used to kill five of the victims, including two children; one woman was shot, police spokesman Anthony Guglielmi said.

Investigators are interviewing a wide range of people, from the kids' dad and their teachers to the adults' co-workers, he said, "looking for what could have been the catalyst for this."

"This was not random," he said. "There's something centered on that family."

The father of Leonardo Cruz, 13, and Alexis Cruz, 10, arrived in Chicago from his home in Morelos, Mexico, on Wednesday to attend Sunday funeral services at St. Gall Catholic Church, said Marcelino Miranda, consul for legal affairs at Mexico's consulate.

The other victims were the boys' mother, Maria Herminia Martinez, 32; Rosaura Martinez, 58; and Noe Martinez Sr., 62, and Noe Martinez Jr., 32.

When authorities discovered the bodies Feb. 4, they saw no signs of forced entry, meaning a home invasion or robbery preceding the slayings is unlikely, Guglielmi said.

Among the questions police are investigating is whether there's any link to drug traffickers. "But do we have evidence of that today? No," Guglielmi said. There's also no evidence any family members were involved in criminal activity, he said.

Investigators are looking for any suspicious activity in the area in the hours and days before the killings in video footage downloaded from surveillance cameras on city buses that pass by, and from other homes' security systems, said Guglielmi.

Investigators met with Mexican authorities at the Chicago consulate this week, he said, and requested assistance as they seek to speak with other extended family members in Mexico.

Miranda told The Associated Press that Mexicans have followed news of the killings closely and that the consulate has taken a special interest in the case.

The father, Manuel Armando Cruz, was granted a U.S. humanitarian visa to fly to Chicago.

Both governments are helping with paperwork to send all six bodies to Mexico, Miranda said. Three adults will be buried in Guanajuato. The mother is from Guanajuato, but will be buried with her children in Morelos.

Said Miranda: "The family decided to keep the kids and the mother together."