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Hundreds of volunteers and officials using drones, aircraft, and off-road vehicles searched Tuesday for a man who went for a run in the San Francisco Bay Area and didn’t return home.

Philip Kreycik, 37, left his Berkeley home Saturday morning and drove to the Pleasanton hills to go for a one-hour run. When he didn’t return home by the afternoon, his wife called the authorities.

Kreycik’s cellphone and ID were found inside his vehicle parked in a lot off Moller Ranch Drive. He is known to wear a smartwatch but the device only has GPS capability when near his phone.

Crews were on their fourth day of searching and officials again used airplanes equipped with infrared technology to detect Kreycik from above to no avail.

“When you look at the different contingencies, the assessment of the entire operation of the last four days, we have come to two conclusions; he’s either incapacitated within the search zone and we can’t find him or he is not here, he is somewhere else,” said Sgt. Ray Kelly, a spokesman with the Alameda County Sheriff’s Office, one of the many agencies searching for Kreycik.

Crews worked into the nighttime hours Monday evening using a heat-sensing drone, equipped with high-tech cameras to try and find the husband and father of two, KGO-TV reported.

“Dogs had a scent on the first day that only went a small distance,” said Lt. Erik Silacci of the Pleasanton Police Department.

That scent was lost down a trail off of Moller Ranch Drive near a water tower. Kreycik is an avid runner who is in great shape and has no known health conditions, friends told the television station.

As of Monday evening, there were 100 people from 13 agencies searching for Kreycik, an energy efficiency analyst. Officials with every Bay Area county were involved in the search. Another 200 people joined friends and family to scour the area, KGO-TV reported.

Many of the volunteers don’t know Kreycik, but wanted to help.

“From one father to another, we both have small kids, two kids … if we were lost we would want a search party out here,” said Suraj Ephirajan who had been searching for four hours when he talked to the television station.

On Tuesday, Pacific Gas and Electric confirmed in a statement that Kreycik works for the utility.

“We continue to be hopeful for his safe recovery and appreciate the efforts of the Alameda County Sheriff’s Office and volunteers to help find Philip,” the utility said.