RIVERSIDE, Calif. -- Authorities are searching for a hiker from Ireland who planned to hike the Pacific Crest Trail from Southern California to Canada.

David O'Sullivan was last spotted in April along the trail in California's Riverside County.

Sheriff's Sgt. Chris Willison said Wednesday that teams are searching on foot, by SUV and with air support.

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The 25-year-old's family has reached out on social media to "trail angels," people known to aid hikers on their trek, hoping someone will remember meeting him.

He was scheduled to meet a friend in May but never showed up.

O'Sullivan has black hair, blue eyes and a thick Irish accent. He was hiking solo with a neon blue backpack.

He left Ireland in March and planned to spend five months on the 2,600-mile trail.