A 24-year-old autistic man went missing on a field trip to Prospect Park Wednesday and police were preparing to search the park lake, sources said.

Michael Yam was visiting the Brooklyn park with a group of developmentally disabled people when he and two others became separated from the group at about 1 p.m., according to law-enforcement sources.

The other two were quickly found, but Yam remained missing.

Police deployed a K9 cop who took Yam’s scent from his mattress at his Crown Heights nursing home and scoured the park for him.

The canine followed the scent to a lake near East Drive, the sources said.

A scuba search team was expected to search the lake early Thursday.

Yam is about 6 feet tall and weighs 112 pounds. He was last seen wearing a gray hoodie and blue jeans.

He also has a lanyard with his name and picture around his neck.