Family, friends, and complete strangers have joined in the search for a missing Delaware County teen, combing the region on foot, by car, and in the air, their movements tracked electronically to ensure no spot is missed.

More than 200 volunteers showed up at Episcopal Academy on Saturday as the search for Cayman Naib, 13, of Newtown Square, entered a third day. The Civil Air Patrol joined in the effort and the FBI was analyzing the youth's cellphone and computer to see whether he had contacted anyone before disappearing.

Naib left home about 6:30 p.m. Wednesday and has not been seen since. His parents theorize he impulsively ran away after receiving a negative progress report from the Shipley School in Bryn Mawr, where he is in eighth grade.

"We are treating this as a runaway we are attempting to locate," said Officer Bill Moor of the Newtown Square police.

Police are interviewing family and friends, monitoring social media, working with county detectives, state police, and other jurisdictions, and are helping the volunteers, he said.

Updates on the search posted on the Find Cayman Facebook page had more than 13,500 "likes" by Saturday afternoon.

Around 12:30 p.m. the boy's parents, Farid Naib and Becky Malcolm-Naib, came into the lower school gym, where searchers were gathered awaiting instructions.

"Your efforts are so helpful and so appreciated," Malcolm-Naib said. She commended the group for getting the word out on social media and for plastering posters of her son all over the region. "It's been incredible."

A visibly shaken Farid Naib said his son had never done anything like this before, leaving his parents and sister Savannah, 15, "really, really worried."

"He disappeared just about into thin air," Naib said. "The disturbing thing is that there has been no sighting of him since Wednesday night."

Volunteers listened earlier as Bruce Newman, a family friend, outlined three search tasks - door-to-door canvassing, ground search, and dog-team support.

Every volunteer was logged in, assigned a specific task, and asked to return to the school to sign out. All were given pink ribbon armbands and asked to download a GPS app so their specific routes could be tracked and recorded.

"We need to know everybody who is here," Newman said.

In addition to the ground search, the Civil Air Patrol was enlisted to cover more territory, Newman said.

With the family's home on Harrison Drive in Newtown Square as the center, the search will spread out in all directions in ever-widening circles in Delaware, Chester, and Montgomery Counties, Newman said.

Search coordinators told volunteers to download and use the GPS app Mytracker, which follows the paths of their cellphones. The information will be collected and entered into a geographic information system map program that will be used to record what territory was covered.

They are trying to keep track of every square inch covered, said Matthew Cohn, volunteers coordinator.

The Civil Air Patrol is covering an expanded search area, and the family said a drone was dispatched Friday to search the grounds of Valley Forge National Historical Park.

Radnor High School teacher Dave Wood, who did not know the Naib family, came Saturday to do whatever he could to help find the teen and bring them relief.

"It's a terrifying thing for kids to be missing," he said.

The number of volunteers who braved the cold impressed Brendan Howard, 40, of Tredyffrin Township.

"It makes me think we have a strong community," Howard said.

Just hours before the season's biggest snowfall began, Naib left home in a cold rain, leaving behind his cellphone, wallet, eyeglasses, and computer, his family said.

Naib, brown-haired and brown-eyed, standing 5-foot-7 and weighing 110 pounds, was wearing a gray down winter jacket, black ski pants, and hiking boots when he left. As much as 10 inches of snow fell in the area into the day Thursday.