A 5-meter (16-foot) crocodile snatched a 26-year-old swimmer in a notorious Australian river as several people celebrating a friend's birthday watched, police said.

The victim and another man crossed the Mary River and were swimming back when the crocodile attacked, Senior Sergeant Geoff Bahnert said.

"Several of the group in the party witnessed the male being taken in the jaws of the croc for a period of time, and then he was out of sight," he said.

The group had been celebrating a friend's 30th birthday on Saturday at the Mary River Wilderness Retreat, an Outback tourist destination 70 miles (110 kilometers) southeast of the Northern Territory capital Darwin.

The victim was from Darwin, but his name was not released.

Police and a government crocodile management team were searching for the man's remains, including dragging the river, Bahnert said Sunday. An officer shot one of the largest crocodiles there for the safety of searchers, but it was not yet known if it was the killer crocodile.

Alcohol may have played a part in the men's decision to swim, he said.

"The Mary River is known worldwide to have the greatest saturation of adult saltwater crocodiles in the world. You don't swim in the Mary River," Bahnert said.

Crocodile numbers have exploded across Australia's tropical north since the species was protected by federal law in 1971. The crocodile population is densest in the Northern Territory and is promoted as a major tourist attraction.

"The advice to tourists is to come, look, take photographs and stay out of the water," Bahnert said.