"ATTENTION, IMPORTANT INFO FOR THE SELECTION OF A RENTER: French nationality obligatory, no blacks..."
So reads the technical notes on a home rental announcement from a real estate agency Levallois-Perret, in the north western suburbs of Paris.
A potential renter saw the ad in late November and shared it on Twitter.
The tweeter wrote: "'No blacks'? What kind of a criteria is that?". His tweet alerted racist and rights groups to the posting.
After no real response at the time, he tweeted it again on Boxing Day, including the names of several high profile journalists.
Before long the advert had made it to the front page of the French news sites, and prompted an apology from the real estate company behind the ad, Laforet.
"We offer our most sincere apologies," the group tweeted on Monday.
The real estate agency's head Laurent Balestra told France Info that the incident had left him shocked.
He said the "naive" employee who wrote the ad no longer works for the company, adding that she had simply "transcribed without knowing" what the house owner had said.
In other words, it was the home owner who was racist, he added, and an "isolated incident" that the owners words made it out into the public.
"If a home owner is racist, I instruct my employees not to take the post," he added.
France's Defender of Rights group said on Tuesday that it had launched an investigation.