DALLAS -- While working a sting to catch unlicensed mobile cosmetologists, an undercover investigator secretly peered out a window to get a glimpse of a possible culprit.

Carla DeRuisseau advertised herself online as a mobile cosmetologist; and Tuesday afternoon, she walked right into a sting conducted by the Texas Department of Licensing and Regulation.

"Licensed cosmetologists, manicurists, barbers - they work very hard to get their license and to stay in compliance,” said licensed cosmetologist Sarah Sandmann. “People like this do them a disservice, and it's not fair."

Sandmann assisted undercover investigators on Tuesday’s sting.

State investigators responded to DeRuisseau's online advertisement and hired her for what she thought was a spa party.

"Nothing came out of a sanitary new sealed bag or case," Sandmann said.

Files, clippers and emery boards that aren't sanitized can spread infections.

"We have no idea how many she's used these on, but by the looks of them they've been used excessively," said an undercover investigator while holding three files that appeared to have not been cleaned in recent times.

The undercover officers said that can lead to big public health issues.

And in fact, it has in the past. News 8 previously reported on Kimberly Jackson in 2006. The mother of three died from an infection after getting a pedicure at a salon.

State investigators said mobile cosmetologists, who advertise online, are a growing worry because they're harder to police and put out of business.

DeRuisseau displayed a valid cosmetology license from Massachusetts, which is where she said she used to live. However, records show she failed the cosmetology exam in Texas in both September and October.

"To be honest to you it was not scary, but it was wakeup call," she said.

With no license and unclean utensils, DeRuisseau packed up and left pledging to take the exam again.

For the unsanitary utensils and not having a license, DeRuisseau will likely face fines that could reach up to $6,000, investigators said.

E-mail jwhitely@wfaa.com