She had been missing since returning to the houseboat moored near the city centre after a party earlier this month.
"There are indications that it is indeed her, but we are awaiting the results of forensic tests before we can confirm it officially," a police spokesman said.
Katoucha, aged 47 and originally from Guinea, was one of the first black African models to become a global catwalk star in the 1980s.
She modeled for designers including Yves Saint-Laurent and Christian Lacroix.
Born Katoucha Niane, she became a campaigner against genital mutilation, a procedure she underwent herself at the age of nine.