NEAR BRUNSWICK, Ga. -- The search for a 6-year-old who has been missing for four days intensified on Monday evening after police received a tip about where the boy might be found.

Police said they received a tip that Christopher Barrios Jr. may be inside the mobile home of a registered sex offender who lives near the home of the boy's grandmother.

The sex offender, whose name was not immediately released, was named a suspect by the Glynn County police.

They said the man has been in jail on a violation of probation charge since last Friday, the day after Christopher disappeared.

Christopher was last seen Thursday night when he vanished from a play area in the Canal Mobile Home Park where his family members live.

Nearly 300 volunteers spent the weekend searching the area, and organizers vowed their efforts would not halt until Christopher was found.

After two days of searching with ground units, helicopters, K-9 officers, mounted patrols and ATVs, the police said they were convinced Christopher is no longer in the area and the Georgia Bureau of Investigation issued a Levi's Call -- Georgia's equivalent to an Amber Alert.

However, at about 8:30 p.m. police showed up at the sex offender home without a warrant, stating they had probable cause to search the residence for the missing boy because a tip came in from a family member of the man who lives in the trailer.

The boy was not initially found, but a short time later police returned to the home with a search warrant and began a more intensive search, which continued through 10 p.m.

"We've not found the boy, but the evidence we have came to us from some of the family members within that trailer that led us to believe that he was in there and alive. So, we made an emergency entry into the trailer to make sure that he was there. It turned out that he wasn't," said Glynn County Police Chief Matt Doering. "We're continuing to search as we speak. I called the state patrol and requested that their helicopter come back out tonight to do an emergency sweep of the area."

The police chief said they were waiting for a helicopter equipped with thermal imaging capability to allow them to search the ground more thoroughly and hopefully find Christopher alive.

Christopher was last seen wearing a blue-green pullover sweater with black pants and white Reebok tennis shoes.

On Friday, the reward for information leading to Christopher safe return was raised to $30,000.

The Glynn County Police Department asks anyone who has seen Christopher or can provide further information to call 912-554-7803 or Silent Witness at 912-264-1333.