Police stepped up their search for a missing drug sales representative after finding the 28-year-old woman's car near an abandoned building in Hammond, Ind.

Nailah Franklin was last heard from Tuesday, when she sent an uncharacteristically vague text message to friends and family saying that she was having dinner and that she'd call later.

She never did.

Days earlier, Franklin had filed a police report saying she had been getting threatening phone calls.

Franklin's sister, Lehia Franklin Acox, said the family is trying to stay positive as police search the car for clues that could shed light on her disappearance.

Being positive "is our only option," Acox said before a weekend prayer vigil.

"We're all just trying to keep our spirits up, but it's a challenge," she said. "This is really taking a toll on us, with every day that passes. We're not sleeping well, we're not eating well."

When Franklin didn't turn up for an important meeting last Wednesday with her boss at Eli Lilly and Co., co-workers at the Indianapolis-based drug company called her family, and family called police.

Franklin's sales territory covered Chicago's suburbs, her sister said.

Acox said it's unusual for Franklin not to contact her friends or family, leading them all to fear that she didn't leave willingly. Franklin had recently filed a police report about threatening phone calls she had received, but she declined to file an order of protection against the alleged offender, a man she once dated.

Franklin's car, along with some personal items, was found Friday night near an abandoned building in suburban Hammond, said Chicago Police spokeswoman Monique Bond. She said the car was being taken to Chicago for forensic and evidence processing.

Several jurisdictions, including Chicago, Hammond, and the Cook County Sheriff's department, were searching for Franklin, Bond said. Divers have also been involved in the search.

Acox said the discovery of the car was heartening because it could yield some clue to Franklin's whereabouts, but "on the other hand, it's still maddening because we do not have (her) back with us."