MOOSE, Wyo. (AP) — Authorities searched Thursday for a Russian college student reported missing after failing to turn up at his summer job in Grand Teton National Park.

Aleksandr Sagiev, 23, was expected back at his job in the deli of the grocery store at Dornan's resort on Monday. He was last seen using his cellphone at the bar of the resort's pizza restaurant the day before, park spokeswoman Jackie Skaggs said.

"It's concerning because he's a very responsible person," Skaggs said.

Searchers have few clues to go on.

Sagiev has spent a lot of time walking and hiking in the park since arriving in June, and rangers are talking to his friends to find out what his routes and habits were, Skaggs said.

Co-worker Nicole Nicklas said Sagiev recently talked about planning a day trip to nearby Yellowstone National Park.

On Wednesday, searchers used dogs and boats along the Snake River near the resort but found no trace of Sagiev. On Thursday, searchers said Sagiev may have been hiking Taggart, Bradley or Delta lakes.

Rangers were methodically searching the area surrounding the privately owned resort, which includes cabins, shops and a gas station.

Dornan's is across the river from the park's headquarters and serves both visitors and residents. Many of its seasonal workers come from Eastern Europe.

It is unclear where in Russia Sagiev is from. His Facebook page says he's studying at the Higher School of Economics, which has its main campus in Moscow.

Sagiev is 5-foot-7, has black hair and brown eyes and weighs about 155 pounds. He was last seen wearing tan shorts and a camouflage shirt.