Park spokeswoman Kari Cobb said Tuesday that emergency services received "multiple calls" about one or more hikers going into the water and over the 317-foot Vernal Falls on the Merced River at around 1 p.m.
Rangers immediately closed the Mist Trail, a popular hike with tourists that leads to the waterfall, and rescue officials sent a member of the park's search and rescue team to the top of the falls while the rest of the team was deployed below.
"They're out there interviewing witnesses, but they still don't have anything," Cobb said at 4:30 p.m.
Park officials often close areas when they feel a body might be recovered. Visitors were traumatized in May when a hiker slipped and fell into the Merced River. His body snagged on a rock and rescuers were not able to reach it for hours.
Record snowfall has created spectacular waterfalls in the park, but it's a treacherous beauty. Visitors often underestimate the force of water, and the mist from waterfalls creates slippery conditions on trails.
At least eight people have died in the park this year, Cobb said. Two men died after being swept off a bridge near the Hetch Hetchy Reservoir in June. One man who disappeared while hiking near Yosemite Falls with his church group is still missing.
The Mist Trail will be closed until at least noon on Wednesday, possibly longer.
The path to the top of Vernal Falls, a three-mile trek with a 1,000-foot rise in elevation, is one of the most popular hikes in the park. At the top a guardrail separates visitors from the treacherous water, and signs in multiple languages warn visitors of the danger created by slippery boulders. Published accounts say that 13 people have died by falling over since records began being kept in the 1920s.
The Associated Press contributed to this report.