A search is underway in Yellowstone National Park for a seasonal concessionaire employee who disappeared while swimming in the Yellowstone River.

Feiyang “Isaac” Xiang, 21, from China was backpacking with four friends on Thursday, July 23 when he disappeared  while swimming in the Yellowstone River near the confluence with Hellroaring Creek in the northern section of the park, according to a news release from the park.

“Xiang was in the water with two of his companions around 11:45 a.m. when he was pulled away from the shore by the current of the swiftly flowing river. Xiang was struggling to stay afloat as efforts to pull him back to shore were unsuccessful. He was swept downriver into a long stretch of rapids before he disappeared from view. A member of the party found spotty cell phone reception and placed a broken 911 call to park dispatch at 12:39 p.m.,” the news release states.

Rangers immediately responded on horseback and on foot. Initial search efforts Thursday afternoon did not turn up any sign of Xiang.

Search efforts were increased on Friday, with approximately 40 people including a helicopter, two dog teams, and 20 Yellowstone and Grand Teton National Park employees actively searching the Yellowstone River corridor.

Xiang is described as 5 feet 6 inches tall, 140 pounds, with black hair and brown eyes.

Anyone with information about the whereabouts of Feiyang “Isaac” Xiang is asked to call Yellowstone National Park at 307-344-2643.