Simon Cowell has remembered former Pop Idol contestant and theatre star Darius Campbell Danesh as “charismatic, funny and just a great person to be with” following the singer’s death aged 41.

Campbell Danesh was found dead in his apartment in Rochester, Minnesota, on August 11, his family announced.

In a statement given to the PA news agency, former Pop Idol judge Cowell, 62, said: “I first saw Darius on television over 20 years ago and I got to know him really well.

“He was charismatic, funny and just a great person to be with.

“His passing, for someone so young, is an absolute tragedy and my heart goes out to his family and friends.”

Following his death, Campbell Danesh’s family issued a statement, which said: “It is with great sadness that we announce the passing of Darius Campbell Danesh. Darius was found unresponsive in bed in his apartment room in Rochester, Minnesota, on August 11 and was pronounced dead in the afternoon by the local medical examiners’ office.

“The local police department have confirmed that there were no signs of intent or suspicious circumstances. The cause of his sudden death is unknown at this stage while medical examinations continue.

“We ask that you kindly respect our wishes for privacy at this time whilst we come to terms with the tragic loss of our son and brother.”

The cause of death remains unknown.

The Scottish singer-songwriter and actor – who was known as Darius Danesh when he made his first bid for fame in ITV show Popstars in 2001 – also appeared on the first Pop Idol, which was won by Will Young.

Gareth Gates, who found fame after finishing as a runner-up on the first series of Pop Idol, paid tribute in a touching Instagram post.

Alongside a picture of himself and Campbell Danesh, the 38-year-old wrote: “I can’t quite believe the news of my dear friend Darius passing. I’m heartbroken.

“Darius took me under his wing during our time in Pop Idol, like a big brother; always looking out for me and for that I thank you my friend.

“I will miss our chats. He was one of the most beautiful, intelligent and gentle souls I was lucky enough to know, a soul that lit up every room.

“Good bye my friend. Forever in my heart x.”

After watching a clip of Campbell Danesh performing a rendition of …Baby One More Time by Britney Spears, record producer and former Pop Idol judge Pete Waterman told TalkTV: “Too young, I mean no age, 41. You’ve got to feel for his parents. This is tragic.

“You watch a clip there and it was a whole different generation of television. It’s unreal.”

He added: “He never got the credit he really deserved about how he worked of Popstars and Pop Idol. He was clever.”

After Pop Idol, Campbell Danesh turned down Cowell’s offer of a record deal and signed with producer Steve Lillywhite, whose credits include U2 and the Rolling Stones.

His debut single, Colourblind, was released in July 2002 and went straight to number one, marking the start of a run of top 10 releases.

He went on to forge a successful stage career, appearing in Chicago as Billy Flynn in two runs of the production, as well as Guys And Dolls, Gone With The Wind and more in the West End.

He lived in the US and found love with Canadian actress Natasha Henstridge, whose films include sci-fi hit Species.

The couple married in 2011 at the San Ysidro Ranch in Santa Barbara, California, but were divorced a few years later.

After coming third in Pop Idol in 2010, he went on to win the first series of ITV’s Popstar To Operastar contest, beating Bernie Nolan of the Nolan Sisters in a close final.

A few months after his win on the ITV show, which featured Welsh singer Katherine Jenkins and Mexican-born tenor Rolando Villazon as judges, he landed his first major opera role as he was cast in a new production of Carmen at London’s O2 Arena.

He took on the principal role of toreador Escamillo in the production, for a one-off performance which marked the first ever opera at the venue at the time.

In 2011, speaking about reprising the role of Chicago’s scheming lawyer Flynn, he said he had based his portrayal of the character on his old mentor and Pop Idol judge, Cowell.

Campbell starred opposite Ugly Betty star America Ferrera in the musical set in prohibition-era Chicago, and said: “He’s the consummate businessman and a wonderful guy and there’s a lot of Simon Cowell in Billy Flynn in terms of the way he approaches things and I recognise that in terms of the character.”

He credited Cowell with persuading him to take on the role in Chicago in the first place.

He said: “I’m incredibly grateful for the experiences I’ve had and all the opportunities that it opened up and to be able to call Simon Cowell a friend and to be able to have dinner with him.”

Campbell Danesh was born in Glasgow to a Scottish mother and Iranian father.

News of his death prompted tributes from the worlds of music, film and television.

Presenter and former member of pop group Hear’Say, which was formed on Popstars, Myleene Klass tweeted: “Everyone should watch this performance. Darius, you were so talented, so kind. A true family man. My thoughts are with them now.x” along with a link to a video of Campbell Danesh performing.

Liberty X member Michelle Heaton, who also competed on Popstars, remembered Campbell Danesh’s rendition of …Baby One More Time in his Popstars audition.

She tweeted: “So sad… thoughts with Darius family right now x always our Britney.”