San Bernardino County and the FBI are offering separate $25,000 rewards for help solving the kidnapping of 3-year-old Briant Rodriguez.
The authorities in California are hoping the public will be able to lead them to the missing boy after a promising lead apparently went nowhere.
On Thursday, authorities released a surveillance photo they believe shows the two Hispanic male suspects in Briant's abduction. They also think the unknown suspects are driving an early 1990s dark green Ford Bronco, seen in a newly released photo. A spare tire is mounted to the back of the truck.
The boy was taken Sunday during a brazen armed robbery. Two gunmen burst through the family's front door and tied up Briant along with four of his siblings and their mother, then ransacked the house, stealing money and other property, the Sheriff's Department said.
The home invasion lasted about 20 minutes, after which the men left with Briant, ordering his mother and the other children not to call police, officials said.
San Bernardino County sheriff's office said Wednesday in a statement they "got a very good lead that the public can help us with," but that tip fizzled.
"It did not prove to be substantial to the case," sheriff's spokeswoman Jodi Miller told the San Bernardino Sun on Thursday. "They will not lose hope."
Detectives say tips have been pouring in, but most weren't yielding any solid information leading to Briant's whereabouts.
No motive had been established and federal and local investigators were looking at several theories, including that the Spanish-speaking kidnappers were from Mexico and may have had ties to organized crime there.
Border authorities were put on alert and FBI agents were helping in the investigation.
The family lives in a modest, single-story home in a lower-income area abutting the city of San Bernardino, about 60 miles east of Los Angeles.
Police are concerned that TV news vans parked outside the family's house might be keeping the abductors from making contact.
One of the children was able to loosen himself from his ties and freed the rest of the family, authorities said.
The Associated Press contributed to this report.