The woman was taken to Mount Sinai Hospital in critical condition after the incident in Brighton Park, according to CPD.
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She has stab wounds to her neck and wrists.
The incident happened just after 10 p.m. in the 3800-block of South Archer Avenue at "Body Health Center."
The business is described as a wellness spa, which offers services like massages and body scrubs.
The business was just closing for the night when police say the 35-year-old female employee was stabbed by a male patron during some kind of altercation.
The circumstances surrounding it are unknown, but the woman was stabbed multiple times.
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Several police units were on the scene overnight collecting evidence inside and outside the business.
As of Thursday morning, the incident remains under investigation by Area One detectives and so far no one is in custody.
The woman has undergone surgery, and remains critical.
The business has surveillance cameras at the front door, which could offer investigators some valuable information.
So far, no one from the business is commenting.
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