LYNN – Police are “actively pursuing” the possibility that someone may have helped Ernesto Gonzalez hide his son Giovanni late Aug. 16 or on Aug. 17, District Attorney Jonathan Blodgett said Tuesday.”We don’t have anybody, but that is our big focus right now,” Blodgett said as the search for the 5-year-old East Boston boy enters its fourth week.”We’re still searching for him as an alive young boy,” he said, adding that police are exploring the possibility someone may have loaned a vehicle to Gonzalez or given him a ride on the weekend his son was staying with him in his 2 Brightwood Terrace apartment.Neighbors said Gonzalez traveled by bicycle and Blodgett said other people who know the 36-year-old machine operator said he occasionally traveled by bus.”We’re actively pursuing if there was someone else who may have been helping him,” Blodgett said.Police are poring through videotape from bus and subway stations for any glimpse of father and son. Searches to date have concentrated on the Lynn area, including the blocks around Gonzalez’ apartment building and wooded areas such as Pine Grove Cemetery.The boy’s mother, Daisy Colon, could not contact Gonzalez when she went to retrieve Giovanni Aug. 17 at Gonzalez’ apartment a half block from Lynn District Court.She called police who questioned Gonzalez in his apartment. He told them he had not seen his son since Aug. 10. They arrested him and charged him with child endangerment after checking Colon’s cell phone and verifying she had spoken with Gonzalez on Aug. 15.Gonzalez is being held in the Essex County House of Correction in Middleton. Despite several requests by police through his attorney to talk with him, Blodgett said Gonzalez has “elected not to speak to us.”He is due back in District Court on Sept. 17.Law enforcement officials have met several times in the past week and drawn up new search targets and lists of individuals they want to talk to in the search for Giovanni.The boy was scheduled to start school in East Boston Monday and Colon has not given up hope that national efforts to highlight Giovanni’s disappearance will provide police with information.America’s Most Wanted has featured the boy on its 9 p.m. Saturday show twice since his disappearance.”We’re talking to law enforcement about doing a bigger piece on him if they think it would help solve the case. We definitely want to help find this little guy,” said Jon Leiberman, the show’s New York correspondent.Clear Channel Communications plans to display Giovanni Gonzalez’ picture and a photograph of his father along with search information on one of its Wyoma Square billboards.”We hope to have it up by the end of the week,” said company spokeswoman Rochelle Cowan.