Authorities fanned out for the second time across a sprawling Los Angeles-area park seeking clues in the disappearance of a 5-year-old boy missing for nearly a month.

The search Thursday at Arroyo Seco Park in South Pasadena came after detectives received a "recent, credible" tip, according to sheriff's Lt. Joe Mendoza. He didn't elaborate.

Crews using dogs and drones scoured a 2-square-mile (5-sq. kilometer) area, rooting through thick brush and examining drainage tunnels.

Investigators previously searched the park after the father of Aramazd Andressian Jr. was found passed out there on April 22. Sheriff's officials said the father acknowledged taking prescription pills and was in a car doused with gasoline, alongside a pack of matches.

On Wednesday, the boy's mother made a heart-wrenching plea for her son's safe return.

"To my son, this message is for you my love: be brave, honey," Ana Estevez said through tears. "I am counting the days until I see you honey and I will never stop looking for you."

Authorities say the boy was last seen April 20 with his father, Aramazd Andressian Sr., leaving Disneyland in Anaheim.

Police began investigating after Estevez reported that her estranged husband had failed to drop off their son at a pre-arranged meeting place. The parents are divorcing and share custody.

The father was initially arrested on suspicion of child endangerment and child abduction but was released days later after detectives declined to present the case to prosecutors.

Andressian told investigators that he was at the park with his son but did not remember what happened to his child or any details that would be useful in locating him, Mendoza said. Authorities haven't been able to confirm the boy was at the park.

The father's attorney did not respond to a message left Wednesday.