Published: Jan 11, 2013 5:29 PM EST
Updated: Jan 11, 2013 5:31 PM EST

COLLIER COUNTY, Fla.- Yesterday marked the four year anniversary of 6-year-old Adji Desir's disappearance. Desir was reported missing after he was playing outside his grandmother's home in Farm Worker Village in Immokalee.

Sergeant Ken Becker of the Collier County Sheriff's Office has been working on this investigation from the beginning. He says the number of leads coming in has slowed down.

"This case, just like any case, whether it's a criminal case or a missing person case, help from the public is always very beneficial," said Becker. "It's as simple as picking up the phone and calling in a lead that we can follow up on and as time goes on, like any case, that's what this case is going to need."

Currently, the Collier County Sheriff's Office is continuing to investigate about 40 missing person cases.

Becker says an investigation is not closed until they have identified where the person is, and in the last six years, they've had 14 recoveries of long term missing persons.