Two women are missing from a small Colorado resort area, according to authorities.

Most recently, Melissa Whitsitt, 34, was last seen on the 100 block of Woodspur Lane in Winter Park, Colorado, the Grand County Sheriff's Office said in a press release.

Investigators determined that an unknown man used Whitsitt's phone to contact people in the Denver Metro Area on Aug. 13 before she vanished, according to the sheriff's office.

"In May, she moved to Colorado to begin a job at Winter Park Resort," Whitsitt's relative said in a Facebook post. "While we've been working with authorities this week, we've been advised to post here in the event that any possible connections and/or contact might help. We sincerely appreciate all prayers for our family."

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Melissa Whitsitt

Most recently, Melissa Whitsitt, 34, was last seen on the 100 block of Woodspur Lane in Winter Park, Colorado, the Grand County Sheriff's Office said in a press release. (Grand County Sheriff)

In what the sheriff's office has described as a separate case, deputies and U.S. Forest Service law enforcement located 51-year-old Svetlana Ustimenko's rental vehicle parked at the Deadhorse Trailhead area off of Grand County Road 73 near Fraser in late July.

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The vehicle, which was set to be returned on Aug. 10, was parked at the trailhead "for an extended period of time" with no sign of Ustimenko. 

Svetlana Ustimenko

Grand County deputies and U.S. Forest Service law enforcement located 51-year-old Svetlana Ustimenko's rental vehicle parked at the Deadhorse Trailhead area off of Grand County Road 73 near Fraser in late July. (Grand County Sheriff)

Local authorities and search-and-rescue teams, including cadaver dogs, have been searching the area since Aug. 11, but they have been unable to locate the missing 51-year-old woman despite dedicating on and off-trail ground rescuers, horses, drones, and more than 750 volunteer hours to find her.

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A man and a dog search on a trail with mountains in the background

Local authorities and search-and-rescue teams, including cadaver dogs, have been searching the area since Aug. 11, but they have been unable to locate the missing 51-year-old woman. (Grand County Sheriff)

"This case highlights the incredible work and dedication of our professional Search and Rescue volunteers from Grand County and our surrounding entities. The family and I are very grateful to them for their courageous efforts," Sheriff Brett Schroetlin said in a Tuesday statement.

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Ustimenko is from Broward County, Florida, and had been diagnosed with a terminal illness. She "was struggling as she tried to cope and was attracted to the Colorado mountains," Colorado authorities said in a press release.

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The sheriff's office said on Monday that the "two cases are not related, and appear to be isolated incidents with no threat to the community."