(NewsNation) — Oliver Calibet, whose brother Albert Calibet, a retired Los Angeles sheriff’s deputy, has been missing for over a week on the Greek island of Amorgos, expressed frustration at the lack of assistance from authorities in the search efforts.

“I’m not seeing anything,” Oliver Calibet said Monday on NewsNation’s “Elizabeth Vargas Reports,” contradicting claims by the U.S. Embassy in Greece that extensive search operations involving helicopters and dogs were underway. “I had to get a lawyer today so that I can actually have a permit so dogs could come and sniff.”

The missing retired deputy is among several foreigners, including Americans, who have died or vanished under mysterious circumstances on Greek islands in the past week. While some cases may be linked to extreme heat, authorities are investigating potential criminal angles.

Albert Calibet, 58, disappeared last Tuesday while hiking on Amorgos, a 49-square-mile island he had visited regularly for a decade. Despite being an experienced outdoorsman, no trace of him has been found, and his belongings are also missing.

“This is not that big of an island. And I don’t know where he’s at. And I just want him back,” Oliver Calibet said. “For me to request the raw data from the cell towers, I had to basically sign a statement saying that I believe a crime has been committed.”

As the search continues, Oliver Calibet questioned the lack of assistance from U.S. authorities, asking, “Why isn’t the US helping me? Why? I understand it’s a different country. But the US should be helping me. That’s what the embassies are for to help us citizens. I’m getting zero help. And I don’t speak Greek.”

A missing American tourist was dead on a beach on a small Greek island west of Corfu, local media reported.

The body of the man was found Sunday on a rocky, fairly remote beach on the island of Mathraki by another tourist. He had been reported missing Thursday by his host, a Greek-American friend. The tourist had last been seen Tuesday at a cafe in the company of two female tourists who have since left the island.

A 74-year-old Dutch tourist was found by a fire department drone on Saturday lying face down in a ravine about 300 meters (330 yards) from the spot where he was last observed last Sunday, walking with some difficulty in the blistering heat.

Dr. Michael Mosley, a noted British television presenter and author, was found dead last Sunday on the island of Symi. A coroner concluded that he had died the previous Wednesday, shortly after going for a hike over difficult, rocky terrain.

On Friday, two French tourists were reported missing on Sikinos, a relatively secluded Cyclades island in the Aegean Sea, with less than 400 permanent residents. The two women, ages 64 and 73, had left their respective hotels to meet.

“To the people here, this is a mystery,” Oliver Calibet said.

The Associated Press contributed to this report.