Rangers search for hikers under Yosemite falls. Reuters

Tuesday at Yosemite National Park, warning signs, a barricade, and people's urging voices were all ignored before all three hikers playing in Vernal Fall were swept over the 317-foot falls.

Hormiz David, 22, of Modesto, Ramina Badal, 21, of Manteca, and Ninos Yacoub, 27, of Turlock were presumed dead from the plunge. They were part of a close-knit community of Christians from the Middle East who have been settling in California's Central Valley during the past century, according to the Associated Press.

After walking the steep 1.5-mile trail to the top of the fall, the three moved beyond the protective guard rail within 25 feet of Vernal Fall's edge.

According to park ranger Scott Gediman,

Basically one person lost his footing and he started to slide down, and the second person tried to rescue him and then the third, reports Reuters.

Gediman did not believe that Yacoub, David or Badal could have survived. It's a 317-foot vertical drop over rushing water. It's not something that somebody can survive, unfortunately, said Gediman. It's a tragic situation.

A witness Jake Bibee told the media, It was no more than five or six seconds of them bobbing in the water screaming before they went over.

We had to watch the fear on their faces as they knew they were plunging to their death. It was awful.

There were many witnesses, said park spokesman Scott Gediman, who said often more than 100 people gather at the top of the waterfall on summer days, according to The Fresno Bee.

Other visitors were pleading with them to come out of the water, said Gediman. But the requests to stay back from the river were dismissed by several hikers in the same party.

Vernal Falls is surrounded by a metal guard rail and signs in several languages warning hikers not to cross the barricade.

After the accident, the Mist Trail was closed on Tuesday afternoon as a search effort was made for the bodies. The trail was reopened Wednesday as rescuers moved to search the downstream.

While Yosemite National Park officials said the search operation will continue at the Merced River, the search itself was extremely dangerous and was being conducted largely on the shore and a footbridge at the base of the falls as crews try to spot the bodies or any clues, such as shoes or items of clothing, says Reuters.

The record snowfall during the past winter has filled rivers with high and freezing flows, making the search difficult.

Ranger and Incident Commander Jeff Webb said that the river swells with a rush of water each afternoon and evening, putting searchers at risk. It is impossible to use search boats, search dogs, and helicopters, according to Webb.

The current search effort by 20 to 30 searchers at the sides of the river will be cut back in the next several days if the bodies are not found, but will be renewed as the flow slows in the coming weeks, reports The Fresno Bee.