Mariska Hargitay shares in documentary that Mickey Hargitay isn't her biological dad

May 19 (UPI) -- Law & Order: SVU icon Mariska Hargitay shares in a new documentary that Mickey Hargitay isn't her biological father like she and the world have long believed.

The actress discussed her parentage in My Mom Jayne, an HBO documentary about her late mom, model and actress Jayne Mansfield.

Mariska, now 61, discovered in her 20s that Italian singer and comedian Nelson Sardelli -- not Hungarian bodybuilder and actor Mickey -- is her actual birth father.

The Hollywood Reporter, EW.com, E! News, the New York Post and Today reported the news.

Also according to My Mom Jayne, which Mariska directed and which screened this weekend at the Cannes Film Festival, Mickey raised Mariska and two of her older siblings after Mansfield died at the age of 37 in a Louisiana car crash in 1967.

Mariska and two of her siblings were in the vehicle at the time.

Mickey, who died in 2006, knew Sardelli fathered Mariska while Mickey and Mansfield were briefly separated, but he never wanted to discuss it with Mariska.

Mickey and Mansfield reunited shortly before Mariska's birth in 1964, but they split up again later that year.

Mansfield would marry and divorce another man, filmmaker Matt Cimber, before she died.

Mariska described learning the truth about her parentage as feeling like "the floor fell out from underneath me," like she was "living a lie" and as though her "infrastructure was dissolved."

Mariska told Vanity Fair she met Sardelli, now 90, when she was 30.

She said she behaved much like the no-nonsense New York Police Department detective she plays on SVU when she approached him after a show in Atlantic City.

"I went full Olivia Benson on him," she recalled.

"I was like, 'I don't want anything, I don't need anything from you. I have a dad,'" she said. "There was something about loyalty. I wanted to be loyal to Mickey."

Sardelli and his family participated in the documentary, which is to premiere on HBO on June 27.