Updated

Police searching for two women who recently vanished in South Carolina came upon a set of human skeletal remains near where a third woman disappeared three years ago.

The discovery came as a reward for missing 20-year-old Heather Elvis, of Myrtle Beach, was increased to $20,000. Authorities intensified their search for Elvis and another young woman -- both of whom disappeared from the same area within a week of each other. While scouring a heavily wooded area for Elvis on Saturday, authorities found "adult skeletal remains," said Lt. Peter Cestare of the Horry County Police Department. It is not yet known whether the bones, which have been there "for some time," are male or female, he said.

The bones were found about 25 miles from where 17-year-old Brittanee Drexel was last seen in 2009. Drexel, a high school junior from the Rochester area, went with friends and without her mother's permission to Myrtle Beach on April 23, 2009. Authorities have long said they suspect Drexel is dead, but exhaustive searches for the teenager have never turned up remains.

"They’ve been there for more than three years, but I can’t give you a timeline," Cestare said of the bones.

Elvis' father has teamed up with the Tilted Kilt corporate offices to increase the reward for information on his daughter, who was last heard from around 3 a.m. Dec. 18 after she went on a date, according to her family. Her car was found abandoned at a boat landing Dec. 19 in Horry County.

"She's a beautiful young lady," the woman's father, Terry Elvis, told FoxNews.com. "She’s a good-hearted girl . . . always helpful and active in her church activities. Everybody loved her."

"To not hear from her for more than 24 hours is way out of character," he said.

Horry County Police and volunteers have spent the last week looking for Heather Elvis, but have found no trace. Several companies have donated billboard advertising to put up pictures and information on Elvis.

Another young woman, 24-year-old Jamie Lynn Cross, was reported missing five days after Elvis. Cross was last seen leaving her Myrtle Beach home in a green Volvo around 5 p.m. on Dec. 23. There is no indication the two disappearances are related, according to authorities.

Elvis is described as being 5 foot, 1 inch tall and weighing about 118 pounds, with brown hair and brown eyes.

Anyone with information on her whereabouts as well as those of Cross is urged to contact the Horry County Police Department at 843-915-5350.

The Associated Press contributed to this report.