Federica Giacomini, who went by the stage name Ginevra Hollander, went missing on February 9th 2013.
The car owned by the 43-year-old porn star was later found with blood covering the seat, Tgcom24 reported.
Police currently searching the waters close to Castelletto di Brenzone, northern Italy, now believe that she was murdered and her body put in a trunk and dumped into the lake, the news website said.
The key suspect was named as her ex-boyfriend, 55-year-old Franco Mossoni. He was arrested in 1978 for the murder of his wife and is currently being treated in a psychiatric ward.
On February 14th last year Mossoni was stopped at the San Bortolo hospital in Vicenza, 100km from Castelletto di Brenzone, waving a pistol around, Tgcom24 reported.