(CNN) -- About 130 trained mountain rescuers returned before dawn Sunday to search for a skydiver who went missing three days ago in the mountains east of Seattle, a spokeswoman for the King County Sheriff's Office said.
"We don't know if he's on the ground. We don't know if his parachute deployed, and he's stuck up in a tree somewhere," Sgt. Cindy West said.
Sunday's search began at 5 a.m., she said.
Kurt Ruppert, of Lake City, Florida, was reported missing Thursday by two friends after he failed to show up at a landing zone, authorities said.
Ruppert was making his second jump from a helicopter above Washington's rugged Cascade Mountains when he went missing, they said.
Authorities believe Ruppert jumped from an altitude of about 6,500 feet while wearing a special jumpsuit known as a "wingsuit," which allows a person to soar and glide before deploying a parachute.
Searchers used the trajectory of the helicopter and cell phone signals from Ruppert's phone to narrow down the rescue area. Authorities did not say how they determined the cell phone signal, and it was not clear whether he attempted to use it or if authorities were able to track the signal another way.
Two friends who shared the price of a helicopter rental with Ruppert did not see whether his parachute opened on his second jump, authorities said.
Ruppert was not dressed for enduring Washington's cold overnight climate in the mountains.
"We still consider this a rescue mission," West said. "We realize that it is cold outside. But we are hoping he is alive and his parachute got stuck in a tree or something."
CNN's Chelsea J. Carter contributed to this report.