Albert Calibet, 59, of Hermosa Beach disappeared more than a week ago while hiking on the Greek island of Amorgos.
His girlfriend and his brother flew out to Greece days ago to also help with the search, but have said they weren't being offered sufficient resources by the local and U.S. governments. Calibet's brother Oliver is appealing to authorities to give him cellphone data to assist with the search.
Los Angeles County Sheriff Robert Luna told Eyewitness News his department is offering resources to help in the search.
Luna says after Calibet retired as a deputy he continued to work at the department's Transit Service Bureau.
At least five foreign visitors to Greek islands have died or gone missing in recent weeks amid a heat wave in the region. Over the weekend, one American tourist was found dead on the island of Meraki.
Calibet was a frequent visitor to the island and an experienced hiker. He was supposed to meet a friend for lunch after his hike, but never arrived. That friend alerted Greek authorities who launched the search.