New York, NY —

Two tenants and a building owner are currently on trial in the Bronx for dividing an apartment. Prosecutors say illegal walls trapped firefighters, causing them to jump to their deaths during a fire in 2005. As WNYC's Cindy Rodriguez reports, illegal housing remains a serious problem that's difficult to weed out.

REPORTER: The Department of Buildings says last year it wrote more than 13,000 violations for illegal housing in response to complaints at nearly 11,000 properties. That's 62 percent more violations than in 2005 -- and those are only the places inspectors could gain access to.

If it has enough proof, the agency can get a warrant to enter a property, but it seldom does. Some housing experts say illegal apartments are difficult to weed out because some tenants are loath to call in problems when it could mean losing their homes. Many also don't realize their apartments are violating housing codes.

In Chinatown recently, dozens of tenants were vacated from illegal apartments, and several complained of no advance warning to find other places to stay. The city referred many of them to the shelter system.

For WNYC, I'm Cindy Rodriguez.