A downtown spa is apologizing to its clients for falling victim to a "sophisticated card fraud" that exposed the financial information of hundreds of customers.

The credit and debit swiping machines at The Elmwood Spa were tampered with last year some time in the spring. About 216 clients of the Bay and Gerrard Streets spa had their information stolen.

The information was used to make duplicate copies of the cards, which were then used for lavish purchases.

Four suspects are under arrest, none of whom were ever employed by the spa.

The spa's Executive Manager Marie Picton said in a letter to clients that this is the first time in 30 years that Elmwood has had its customers' information compromised.

"We are committed to ensuring it never happens again," she said.

Picton said employees of the spa have been co-operating with the police and credit card companies during the nine-month investigation.

"We were advised by the credit card company that our job was to notify the police and that the credit card company would contact their customers, as we at Elmwood Spa had no way of knowing who those people were," she said in the letter. "The credit card company advised us that they would manage the investigation and ensure all fraudulent charges were rectified for their customers."

The Elmwood has retained a private firm to consult staff on additional security measures that can be implemented at the spa.

"Elmwood Spa takes its customers' security very seriously and we have taken every precaution to safeguard customer data and protect their privacy," the letter says.

Late last week, officers from 11 Division and 14 Division's fraud office executed six search warrants, mostly in the Yorkville neighbourhood.

Police say they seized about $285,000 worth of property, including some furniture and equipment from the Jung Spa on Danforth Avenue.

Goran Sadic, 44, and his 41-year-old wife Milena Sadic, have been charged along with Filip Djukic, 38, and Julia Sung, 25. The four suspects face hundreds of fraud-related charges.

Police say further charges are pending as the investigation continues.