WAIMEA, Hawaii >> An aerial search for a Nebraska man missing in Hawaii has been suspended, but volunteers planned to continue searching for him on the ground today.

Samuel Joseph Martinez, 23, was studying microbiology at the University of Nebraska-Lincoln before he flew to the Hawaiian island of Kauai on May 12 with plans to spend nearly two weeks hiking and camping.

His family hasn’t heard from him since a few hours after he landed on Kauai, his father, Ted Martinez, said last weekend.

Samuel Martinez had eight permits to camp at different locations around Kauai.

Ted Martinez said the family, of North Bend, Nebraska, filed a missing persons report with Lincoln Police last Wednesday, a day after Samuel Martinez missed his flight home.

Extensive land and air searches began Sunday with a focus on Kokee and Waimea state parks, including the Kukui Trail, Sugi Grove, the Alakai Trail and Kalalau Beach, The Garden Island reported.

The fire helicopter checked inaccessible western and northern regions of the island, the newspaper reported.

Searchers identified the location of a pasture on the way to Kokee that Samuel Martinez took videos of on May 13, one of his last known locations.

Rescue crews on Sunday and Monday handed out flyers and spoke to hikers. Police drove all-terrain vehicles through the Waimea Valley and spoke with campers and hunters, police said.

A Waimea Big Save market employee reported having seen Samuel Martinez, but could not provide a date and time of the sighting. The GPS location and footage from this cellphone, are being accessed, Ted Martinez told the newspaper Monday.

Investigators tracked cell phone pings from Samuel Martinez’s cell phone at about 4:40 p.m. on May 12 near Waimea Canyon Drive Road, police said. The last ping obtained was at about 8:20 p.m. in the same general area of Waimea and Kokee state parks.

“Unfortunately, we haven’t found any sign of Mr. Martinez throughout our searches. We also haven’t encountered anyone who has accurately identified him and his whereabouts,” said Kauai Police Department Investigative Services Bureau Assistant Chief Bryson Ponce.

Ponce added: “At this point, there are several possibilities that could have taken place, especially on an island with dangerous terrain in places like Waimea Canyon and Kokee State Park trails, but we are still hoping for the best.”

Martinez had a black Osprey hiking backpack, a gray and green Kelty Salida Camping tent and bright green sleeping bag, according to photos provided by his family.