Updated at 7:59 a.m. ET: NORTH BEND, Wash. -- Rescue crews on Sunday suspended their efforts to find a Florida skydiver outfitted in a wing suit, who disappeared after jumping from a helicopter Thursday afternoon.

Kurt Ruppert, 29, of Lake City, Fla., is a seasoned skydiver, according to a friend, and when he disappeared he was wearing a brown-and-green jumpsuit that has swaths of fabric beneath the armpits that allow the wearer to glide like a flying squirrel.

About 145 volunteers over the weekend canvassed a nine-mile area near North Bend, Wash., that includes 4,200-foot Mount Si, the steep flanks of which are covered with trees. The peak is popular with hikers even though the last summit scramble can be treacherous. At the foot of the steep side of the mountain is the flat, sprawling Mountain Meadows Farm.

Ruppert was skydiving with two friends, and they were taking turns jumping from the helicopter. The friends were waiting at a grassy landing area, but no one saw whether Ruppert's chute deployed.

"The guys on the ground could not see where he jumped from their angle, and the pilot couldn't see when he went out the door because he was focused on flying," said King County Sheriff’s spokeswoman Cindi West.

Ruppert’s parachute was blue, West said, but she said she was told that wing-suit fliers don't deploy parachutes until they reach an altitude of 2,000 feet.

"The speed and height of the jump would enable him to travel a large distance in a short amount of time," West said.

As rescue teams searched, officials tracked his cell phone and flight pattern to better discern where he might have fallen. Nineteen agencies assisted in the rescue effort.

Authorities know the flight pattern of the aircraft, but a number of factors have made it difficult to find Ruppert.

"It's dangerous and difficult,” West said. “The footing is bad and there are lots of cliffs."

Ruppert isn’t dressed or equipped to stay out overnight, authorities said.

Ruppert has been skydiving seven or eight years and is good at handling a wing suit, said a friend, Art Shaffer, owner of Skydive Palatka in Palatka, Fla.

Shaffer jumped with Ruppert at midnight on New Year's Eve and said Ruppert left Tuesday to jump with friends in Washington.

Ruppert is single and once owned a landscaping business, said Shaffer, who is in contact with Ruppert's family and friends.

"We've got our fingers crossed," he said.

The search resumed Sunday morning at the Mount Si trailhead in North Bend, Wash.

This article includes reporting by The Associated Press and NBC News' Isolde Raftery.

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