PLEASANTON (CBS SF) — The search for a jogger who went missing on Saturday near Pleasanton Ridge Regional Park continued Monday night with the help of an infrared drone. The operation has grown to include 13 agencies and nearly 200 volunteers, according to officials.

The Pleasanton Police Department identified the missing jogger as 37-year-old Philip Kreycik. He was last seen on Saturday at around 10:45 a.m. near the regional park while preparing to go on a run.

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Police told reporters Monday, the coordinated search has split the large group of volunteers into 20 teams to comb the area. By Monday night the staging area was quiet, and Alameda County Sheriffs Department was taking over the search effort, using a drone equipped with infrared cameras.

“We’ve got a good picture here during the daytime. As it cools off at night, your body temperature is different than what the ground temperature would be, so it just picks it up better.

The sheriff department’s search plane will also be making passes over the ridgelines all night, using similar infrared technology. A cow in a pasture shows up on a screen, its body temperature similar to a person. Searchers hope to see Kreycik on the screen overnight.

“Our hopes are high. We are still in a search and rescue mode and that’s what we’re going to continue to do throughout tomorrow. Obviously time is important and we want to try to locate him as soon as possible,” said Pleasanton Police Lt. Erik Silacci.

Earlier Lt. Silacci told reporters, “We are still optimistic about locating Mr. Kreycik. Our thoughts are with the Kreycik family and we are thankful for the ongoing support from local agencies and residents.”

Kreycik was reported missing by his wife after he failed to return from his run in the hills near the Moller Ranch staging area in Pleasanton. Kreycik parked his vehicle at the staging area around 11 a.m. and told his wife he was going for a one-hour run in the East Bay Regional Park.

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As search and rescue crew members combed the regional park on Monday as part of the official operation, across the parking lot, friends and family of Kreycik staffed their own staging area directing more than 200 volunteers who were searching for him, as well.

“Philip was my manager at work, so I had to come help,” said volunteer Michelle Levinson.

Levinson and her mother spent the day crisscrossing through ravines looking for any sign of Kreycik — someplace he could have gone to find shade, shelter or water.

“It’s a huge park. We were amazed at how huge it is. There’s so many ravines, so many bushes and trees that he could be behind, so the more people who are canvasing the park, the better,” said Micki Callahan, another search volunteer.

Officials said if the aerial search and rescue crews from the Alameda County Sheriffs Department were not able to find Kreycik overnight, the crews on the ground will be heading back out Tuesday morning.

Kreycik, a Berkeley resident, was described by police as a white male with a thin build, brown hair and brown eyes. He is presumed to be wearing running attire and is an avid long-distance runner with no known health conditions.

Anybody with information about Kreycik’s whearabouts is asked to contact the Pleasanton Police Department at (925) 931-5100.

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Katie Nielsen contributed to this report.