Virginia authorities said Wednesday that a missing firefighter called out sick before not showing up to work last Friday, adding to the mysterious circumstances surrounding her disappearance.

Nicole Mittendorff, 31, last made contact with her family on April 13 -- the same day she called out sick -- before being reported missing. Her car was found Saturday at Shenandoah National Park, launching a massive search.

Fox 5 DC reported Wednesday that Mittendorff's family believes that her disappearance might have something to do with files she downloaded from her cellphone. Legal teams persuaded her phone carrier to hand over the files to authorities in hopes it will provide some indication into where Mittendorff may have gone.

Her family said Mittendorff, an avid runner and triathlete, might have been training on a trail near where her car was found.

“As you can imagine, the pain of not knowing where a loved one is can be unbearable," the woman's husband, Steven Mittendorff, said Tuesday at a news conference.

Fairfax County Fire Chief Richard Bowers urged anyone with information to come forward.

"We want to focus on bringing Nicole home safely," he said at the news conference at the fire station where Mittendorff works, just across the Potomac River from the nation's capital. "This is our 911 call to the public."

Virginia State Police said they’ve received more than 100 tips related to Mittendorff's disappearance, while investigators are still working to develop a timeline from when she last made contact with her family to when officials found her car.

Fox 5 DC reported that federal, state and volunteer teams have spent days scouring the park for any signs of Mittendorff. The TV station reported that federal money has also been given to the search effort.

Virginia State Police spokeswoman Corinne Geller said there is no indication of foul play.

She was also recently reassigned from Station 30 to Station 32 in Fairfax County, sources told the station. However, the fire department wouldn’t confirm whether she was reassigned.

On Tuesday, Bowers lavished praise on Mittendorff, a three-year veteran of the fire and rescue department.

"She's dedicated, she's respected and she's well-liked among her peers and colleagues," he said.

Mittendorff is described as a white female about 5-foot 6-inches, weighing 125 pounds. She has blonde hair and green eyes. Authorities urge anyone with information about her disappearance to call 703-803-0026 or #77 on a cellphone or email information to questions@vsp.virginia.gov.

The Associated Press contributed to this report.

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