Their spokesperson has insisted that their split was a mutual decision and their relationship had just run its course.
But reports today have suggested that actress Mila Kunis could have played a part in Justin Timberlake and Jessica Biel's break-up.
Stories in the US have claimed that the Black Swan actress and the pop star have been 'flirting' with each other since September when they met on the set of their upcoming film Friends With Benefits.
And even though nothing is believed to have happened then, friends have said that Timberlake, 30, is 'very interested' in Kunis, 27, and they have great chemistry.
Speaking to E! Online, a source said: 'Justin is very interested in Mila. They've been flirting. But so far nothing has happened.'
Another source told celebrity blogger Perez Hilton that the pair had been very 'flirty' with each other on set, leading him to suggest that something may now happen between the two now that Timberlake is single again.
The two also joined forces to present an award at last year's Oscars and to some observers, their 'giggling chemistry' was all too apparent.
And they gushed about each other on the red carpet, with Timberlake telling E! Online's Marc Malkin that shooting sex scenes with Kunis wasn't a hard thing to do.
He said: 'That's an easy thing to do. I think I could speak for all the men in the world when I say that's the easy part.'
And her praise was just as gushing when she spoke about him to MTV at the Cosmopolitan's Fun Fearless Males party last Monday.
She said: 'He's just as lovely, just as professional, just as sweet and amazing, and there's nothing that he can't do.'
Timberlake and Biel announced their split yesterday after four years together.
Meanwhile, Kunis split from Home Alone star Macaulay Culkin in January after an eight year relationship.
