Family members said Tuesday afternoon that there are still no clues in the mysterious disappearance of 31-year-old Crystal Morrison Prentice.

The mother of one has been missing since Aug. 23, when she left her job at Connextions Recruiting in Kannapolis, N.C. That day, a co-worker spotted her walking away from the business complex, but there has been no sign of her since.

"When I wake up every day and realize how many days she has been missing, it's overwhelming," Prentice's sister, Mechelle Morrison Carey, told The Huffington Post.

On the day she went missing, Prentice called a family member from her office phone at 12:41 p.m. to ask for a ride home. A friend had borrowed her car that morning and Prentice said she was feeling ill. The family member arrived about 20 minutes later, but Prentice was gone. Her superiors said she did not tell them she was leaving.

"Because she works customer service at the call center we have a recorded call of the conversation," Carey told HuffPost. "She did not say anything out of the ordinary other than she was sick. She gave very specific directions to the building."

RELATED: CRYSTAL MORRISON PRENTICE PHOTOS

A co-worker later told police they had seen Prentice at about 1:00 p.m. that day, walking on International Drive near the intersection with Davidson Highway in Concord, N.C., though where she may have been headed remains unclear.

Authorities have interviewed everyone closely associated with Prentice and have conducted several ground searches. So far, all efforts have proven fruitless.

"The Concord Police Department has searched the area where she was last seen three times. They used dogs and everything else. We also have about 100 volunteers out there. I think we can say with certainty she is not in that area anymore," Carey said.

According to her sister, Prentice has no known enemies. She has been divorced for several years and her ex-husband lives in another state.

Investigators said that, as of now, there is no evidence that a crime has been committed.

"There are no indications of anything criminal other than the fact that she hasn’t been heard from in two weeks," Concord Deputy Police Chief Allen Overcash told HuffPost.

"This is a very unusual case for us -- the circumstances surrounding her disappearance and that fact that there is nothing to go on," Overcash added.

Prentice has an 8-year-old son who lives with her. Carey said the child means the world to her sister and that she would never abandon him.

"She has never, ever left her son before, not even for 24 hours," she said. "It's been 19 days since that little boy has had his mom. She did not get to walk him into school on his first day of third grade and she's never not been there for something like that."

Carey said her family has gone through "every crazy theory," including her sister being ill with a fever or the possibility that she may have been abducted.

"We're desperate," she said. "She is obviously a very beautiful woman and we’re worried that someone might have her. It's very scary for us."

The situation is also dire because Prentice has asthma and requires daily medication and an inhaler.

"That's another big concern for us," Carey said. "She needs that medicine and she did not have very much of it with her."

Prentice did not have her cell phone the day she went missing. The person who borrowed her car also had her phone and was supposed to purchase additional minutes for her. She did, however, have her purse and her identification.

Prentice is about 5-feet, 2-inches tall and weighs 100 pounds. She has blonde and red hair, blue eyes, wears contacts and has piercings in her ears. She has her son's name, "Kyson," tattooed on the back of her neck. She was last seen wearing a white blouse with black flower print, black dress pants, black open-toe high-heel dress shoes and carrying a small black purse.

Anyone with information should call the Concord Police Department at (704) 920-5580. Prentice's family has also established a Facebook page for updates and information about the search.

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    Crystal Morrison Prentice is about 5 feet 2 inches tall and weighs 100 pounds. She has blonde and red hair, blue eyes, wears contacts and has piercings in her ears. She has her son's name, "Kyson," tattooed on the back of her neck. She was last seen wearing a white blouse with black flower print, black dress pants, black open-toe high-heel dress shoes and a small black purse. Anyone with information should call Concord Police at 704-920-5580. Prentice's family has <a href="http://www.facebook.com/pages/Help-Find-Crystal-Morrison/340862109339421" target="_hplink">established a Facebook page about the search</a>.