By Sean Gardiner and Alison Fox

A massive search effort is underway for a 9-year-old boy who went missing after leaving his summer camp in Brooklyn’s Borough Park neighborhood on Monday afternoon.

Leiby Kletzky was last seen leaving the yeshiva where Nechmod Camp is held, located at 1205 44th Street in Brooklyn just before 5 p.m. Monday, police said.

Bob Moskovitz, a member of the Flatbush Shomrim Safety Patrol, said people in the community have been searching for the 4-foot tall, 50-pound boy since around 8 p.m. Monday evening. A Shomrim command center with food and water has been set up on 15th Avenue and 57th Street.

Moskovitz estimated that anywhere between 1,000 and 2,000 volunteers have joined the search so far. To coordinate search efforts, the neighborhood safety patrol has been handing out grid cards that assign each volunteer a two-block area to search, he said.

“They haven’t stopped for one minute,” Moskovitz said of the response from volunteers. “I cannot hand out the grids fast enough.”

New York Police Department officers using helicopters, horses and search dogs have also been canvassing the area, so far without success.

Moskovitz said the searchers have covered a 10-square-foot area from Borough Park into Flatbush twice since Monday night. “But unfortunately we’ve hit a brick wall,” he  said Tuesday afternoon.

The searchers have looked in streets, alleyways and stores, but Moskovitz said they have not yet entered homes. According to the boy’s family, Leiby doesn’t have a history of being a runaway and is in good physical and mental condition, Moskovitz said.

State Assemblyman Dov Hikind said that pledges from local residents and businesses had increased the initial $5,000 reward for information about the boy’s whereabouts to $100,000.

Shomrim officials are also handing out cards with information about Leiby, including what he was last wearing: a blue shirt with green and white stripes, blue pants, black belt, black socks and sneakers and a blue backpack with a “Nechmod Camp” logo.

Pearl Tyrnauer, a friend of the boy’s family, said that Leiby is a “very friendly boy.” He described Leiby’s mother as an over-protective parent who would assign one of her older daughters to accompany the boy if he wanted to go the park to play.

Tyrnauer said that her husband spoke with Leiby’s parents, who said their son had walked home from camp with another student on Monday. The student’s home is about a block away from Leiby’s, and that’s where the two children parted ways.

Tyrnauer said that Leiby’s mother often met him near the friend’s home after school. But when she went to meet her son yesterday, Leiby wasn’t there.

Police say that at this time there is no evidence of foul play.

“We can’t speculate at this time” about foul play, said Moskovitz, the safety patrol official. “Why think the worst? We would like to be optimistic.”