Scores of police officers, firefighters and volunteers searched Friday for a 5-year-old boy with autism who wandered away from a New Year's Eve party barefoot and coatless.

Jayliel Vega Batista was last seen about 11 p.m. Thursday running near an intersection in Allentown, police Capt. Tony Alsleben said.

Jayliel, of Allentown, had been at a party and was playing with a toy when he "left out of nowhere," his 16-year-old sister, Tayritza Molina, told The Morning Call of Allentown on Friday. She said he does not typically run away.

"We're scared, but we're trying to keep positive thoughts in our head," she said.

Private search-and-rescue teams joined the hunt for Jayliel. The searchers were using dogs and two helicopters. A bloodhound picked up a scent and followed it, but police couldn't confirm it was that of the missing boy.

The temperature in Allentown, in eastern Pennsylvania, on Friday was in the 30s, with the wind chill at times making it feel as much as 10 degrees cooler.

Authorities said the boy should not be approached because he is likely to run from strangers.

"He is afraid of people, so we're asking the public that if they do see him, that they not call out his name, just to call us immediately," Allentown Police Chief Keith Morris said.

Police tried luring Jayliel with music played on a truck because he likes lullabies. Residents also distributed papers with the number 7 printed on them — the start of the boy's address — because he responds to it.

The Allentown Police Department's Facebook page asked residents to "check and re-check their properties," especially porches, sheds, garages and other spaces where the boy might have sought shelter.