Chicago police ramped up search efforts for Julian around the neighborhood where Hudson grew up and transferred custody of a "person of interest" in the killings to state authorities.
"Detectives are working 24 hours on this case," said Chicago police spokeswoman Monique Bond. "There's a lot of forensic evidence. We have to work the evidence and try and solve this case. Most importantly, we want to find the child."
- Video:Reward offered for Jennifer Hudson's nephew
- Video:Community prays for victims, looks for missing boy
- Video: Suspect's background
- Video: Community reacts to murders
- Interactive Map: Satellite view of murder scene
- Slideshow: Jennifer Hudson's career
The Amber Alert listed William Balfour, the estranged husband of Jennifer Hudson's sister, Julia Hudson, as a suspect in a "double homicide investigation." Julia Hudson is the missing boy's mother.
Authorities said the search for Julian would be citywide, but on Sunday residents and officers focused their efforts "in the immediate vicinity" of the family's home in the Englewood neighborhood, said police spokesman Dan O'Brien.
Police said they did not have a motive for the killings but called the case "domestic related." Bond said Balfour had not been charged.
"There's a lot of forensic evidence. We have to work the evidence and try and solve this case," Bond said Sunday. "Most importantly, we want to find the child."
Bond said no weapon had been found at the Hudson home, a three-story house sandwiched by vacant lots littered with trash. Investigators on Sunday moved in and out of the home and examined the trash.
In a statement Sunday evening from publicist Lisa Kasteler, Jennifer Hudson appealed to the public for their help, offering the reward and asking that any information be given to Chicago police.
"Jennifer and her family appreciate the enormous amount of love, support and prayers they have received while she and her family try to cope with this tragedy and continue the search for Julian," the statement said.
Mourners stopped by the Hudson home, many laying teddy bears along the chain link fence around the property. Others signed a cross that rested on the fence.
"We love you," one message read. Another said, "We'll find the people who did this."
Police officers were instructed to place fliers with Julian King's picture and description in every business in the area.
Jennifer Hudson, who won an Academy Award for best supporting actress in 2007 for her role in "Dreamgirls," was in Chicago with her family during the weekend, her sister said. A publicist did not disclose her whereabouts, but the Cook County medical examiner's office confirmed she had idenitifed the bodies of her mother and brother.
In a MySpace blog entry on Sunday, Hudson said she was grateful for community support and posted a picture of her sister's son.
"Thank you all for your prayers and your calls. Please keep praying for our family and that we get Julian King back home safely," the blog entry said.
Bond said Balfour, who had been in police custody since Friday, was transferred Sunday to the Illinois Department of Corrections "based on his active parole violation unrelated to this investigation."
Records from the corrections department show Balfour, 27, is on parole and spent nearly seven years in prison for attempted murder, vehicular hijacking and possessing a stolen vehicle.
Corrections spokeswoman Januari Smith said Balfour would likely remain in state custody until the Illinois Prisoner Review Board looked at his case. She would not say exactly where Balfour was being held.
It was unclear if Balfour had an attorney to speak for him Sunday, but his mother, Michele Balfour, has denied he was involved the killings or in Julian's disappearance.
During a public plea Saturday for the boy's return, Julia Hudson described her son as a smart, sensitive and easygoing child. She said she last saw her son Thursday night when they went out to dinner to celebrate her 31st birthday.
Afterward, she said, she took Julian to the home she shared with her mother and brother and handed him to his grandmother, and everyone went to sleep.
Julian King is 7 years old, 5 feet tall, 135 pounds, and has a medium black complexion.
Investigators are also still searching for Jason Hudson's SUV, a 1994 white Chevy suburban with license plate number X584859.
If you have any information about the case or missing child Julian King, you are asked to call the Area 1 Special Victims' Unit 312-747-8385.
Associated Press writer Sophia Tareen contributed to this report.------
On the Net: http://www.myspace.com/jenniferhudson