One of the city's largest nonprofits serving homeless Portlanders sent warning letters this week to clients who might have had their tax refunds stolen by a former employee.

Central City Concern provides Portland's homeless with healthcare, recover resources, and transitional housing, and helps them find permanent housing and jobs. The letters warned that the former employee may have filed fraudulent tax returns between 2010 and 2013 using the information of clients who had used its Employment Access Center.

Central City Concern employs more than 700 people on a budget of about $43 million a year, according to its tax filings. It sent warning letters to anyone whose financial records it still maintained, although law enforcement officials have told the nonprofit they only knew of 15 clients who had been cheated.

"We are taking this matter very seriously and we deeply regret that this incident has concerned," Clay Cooper, director of social enterprises and employment services, wrote in the letter. He said the nonprofit is working with law enforcement. 

Kathy Pape, a spokeswoman for Central City Concern, said this is the first time since the nonprofit opened in 1979 that identity theft has been a problem. "Our staff are really upset that something like this would happen," she said. "This incident was very specific to the employment access center. Not housing or healthcare."

Here's the letter CCC sent out: