PORTLAND - City police Detective Brent Christensen figured the cases seemed "too Hollywood."

In July, a 21-year-old woman bleeding from a stab wound burst into a bank and screamed that she had been robbed. She later told police a knife-wielding man attacked her and stole the money she was trying to deposit for the McDonald's restaurant she managed.

Five months earlier, the manager of Elmer's restaurant in northeast Portland found the night manager bound in a back office. "We were robbed!" screamed the 20-year-old woman.

The cases drew plenty of attention in the Portland area, but the stories started to crumble after the cameras left. Police now say they weren't dealing with violent robberies at all, but hoaxes meant to disguise embezzlements.

Detectives say they're been seeing an increase in such false reports. For a while, robbery detectives joked they were the "internal theft unit."

In the July robbery, Gilda Garcia Ayon reported she was stabbed by a robber with a Latino accent who had stolen a deposit bag she was taking to the bank for McDonald's.

She told police she left McDonald's with $6,000 and first drove to Beaverton because she had to make a car payment.

Ayon told police that when she reached the bank a man appeared as she got out of her vehicle. He punched her in the head and demanded the bag. When she refused, she said he scratched her arms with a knife and stabbed her in the stomach.

Investigators were quickly skeptical. "There were so many holes in this gal's story," Detective Chris Traynor told The Oregonian newspaper.

Detectives thought it strange that Ayon would drive out of town with the cash before making her deposit. Then detectives learned that Ayon hadn't made her car payment in Beaverton until the day after the alleged robbery. The state medical examiner said the cuts looked self-inflicted.

On July 15, the detectives asked Ayon to re-enact the robbery. Police said her story changed. Now she said she was attacked on the sidewalk, not at her car door. Ayon also refused to take a polygraph.

Police plan to take the case to a grand jury to obtain a criminal indictment. Ayon could not be reached at her Aloha address, and a neighbor said she may be visiting family in Mexico.

In the Elmer's incident, Damaris Rose Dunn told police she was closing when a masked man forced her into the office at knifepoint. Christensen said it at first seemed like a terrible ordeal, but questions arose.

Detectives, for example, found it odd that Dunn was not able to free herself from the duct tape because she wasn't bound by thick layers. And a week earlier, co-workers told police, Dunn mentioned that it would be easy to rob the place.

Two weeks into the investigation, police asked her to take a polygraph test. Dunn refused and blasted the investigators for trying to victimize her again.

A Multnomah County grand jury recently indicted Dunn on a charge of aggravated theft. A warrant is out for her arrest.

"I had to put all my cases on the back burner to find out she was the one who actually did it," Christensen said. "That especially makes one upset."