TRENTON -- They looked like any other ad on Craigslist. Great apartment! Free parking. References required. No smoking. No pets.

But authorities say the next item crossed a line.

"No Section 8."

The state Division on Civil Rights on Wednesday sent more than 30 "cease and desist" letters to New Jersey landlords and property managers they say ran afoul of housing discrimination laws by telling those who receive federal rental assistance they need not apply.

State authorities say advertisements like this one violate housing discrimination laws. About 30 landlords and property managers received warning letters from the Division on Civil Rights for posting similar ads.

Section 8, named after a section of a 1937 federal housing law, is common shorthand for the government subsidies given to low-income residents to help pay their rent.

State and federal law prohibit refusing housing to anyone based on a legitimate source of rental income. But according to the state Attorney General's Office, civil rights investigators found a series of postings on Craigslist, the popular classified ad website, doing exactly that.

Christopher Porrino, New Jersey's attorney general, said people who receive government assistance "are not second class citizens."

Lee Porter, who runs the Fair Housing Council of Northern New Jersey in Hackensack, said housing ads telling public assistance recipients not to come knocking are nothing new.

She said her own organization routinely sends similar letters to landlords posting "No Section 8" advertisements.

"Some of them don't even know it's against the law," she told NJ Advance Media. "I think there's a negative perception out there that the people who have the Section 8 are not quite worthy. That's a prejudice some people have."

State authorities say Craigslist recently agreed to amend its fair-housing disclaimer to explicitly state that New Jersey law prohibits refusing housing based on income source as a result of their inquiry. The company did not respond to messages seeking comment.

Craig Sashihara, the director of the Division on Civil Rights, said the state was putting landlords on notice that those "who insist on denying housing to such applicants -- or who discourage them from applying through their advertising -- do so at their own risk."

The letter sent to landlords warns that violators of New Jersey's Law Against Discrimination face a penalty as high as $10,000 for the first offense, and as high as $50,000 for repeat offenders.

Porter said those who rely on public housing assistance come from all walks of life, from working families and single parents to college students trying to get a leg up in a crowded New Jersey housing market where rent is on the rise.

"It's everybody," she said. "It could be you tomorrow and it could be me tomorrow."

S.P. Sullivan may be reached at ssullivan@njadvancemedia.com. Follow him on Twitter. Find NJ.com on Facebook.