The FBI and more than two dozen other agencies descended on a sprawling North Carolina park Monday as the desperate search for an autistic, nonverbal child entered its third day.

Maddox Ritch, 6, was with his father and another adult when he ran off and disappeared Saturday in Rankin Lake Park, a 240-acre recreational jewel 20 miles west of Charlotte that features an 80-acre lake.

Gastonia Police Chief Robert Helton said Maddox's family was working closely with authorities.

"We are all working around the clock with one goal in mind, and that is to find Maddox and to bring him home safely," Helton said Sunday, adding that "every second counts when a child is missing."

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Officers have been aided by volunteer searchers as well as drones and a helicopter sweeping over the park and nearby environs.

FBI special agent Jason Kaplan said the FBI brought in a Child Abduction Rapid Deployment Team that is specially trained for tracking down missing kids. No Amber Alert had been issued because the case did not meet the criteria, Kaplan said without further explanation.

"We are going to explore all possibilities, including abduction, but we are also going to search every inch of the land around here to make sure that he is not simply lost," Kaplan said.

Kaplan said it's not uncommon for special needs children to get lost or be missing.

"It’s something we deal with, unfortunately, with some frequency so the FBI has special resources,” Kaplan said. “We deal with local resources, sometimes we talk with specialists and generally the family is part of that resource, and the most useful, because they let us know what the child may respond to.”

Helton urged area residents to notify authorities if they had seen anything out of the ordinary.

"No piece of information is too small," Helton said. "Our focus is to find Maddox as quickly as possible and to bring him home."

Contributing: WCNC-TV Charlotte