Jun 3, 2011 11:40 GMT  ·  By

Despite earlier reports stating how serious things were getting between Sean Penn and Scarlett Johansson, it seems the relationship stopped working at some point: the two are no longer an item, it has emerged.

When the two failed to appear on the red carpet together at the Cannes Film Festival for the premiere of the much-hyped “Tree of Life,” in which Sean Penn plays Brad Pitt’s son, people started talking about whether they were still together.

They aren’t anymore, People magazine informs.

“Scarlett Johansson and Sean Penn are no longer dating, a source tells People. Speculation about the pair began after Johansson did not attend the Cannes Film Festival with Penn for his movie The Tree of Life,” says the celebrity publication.

“She has been working on The Avengers in New Mexico, reprising her role of Black Widow from Iron Man 2,” the report further notes.

No one seems to know yet what caused the breakup; People tried to contact reps for both Johansson and Penn but, at the time of writing, it still got no response from them.

One problem with the relationship, word online has it, could have been the fact that Johansson came off as too needy and too clingy, constantly pressuring Sean for something more serious.

In April this year, for instance, reports were saying she had moved into his house, and that they were so head over heels in love that they couldn’t find it in themselves to spend any time apart.

A short while afterwards, in mid-May, after Scarlett’s rep denied that she was pregnant, came another rumor: she wanted to have Sean Penn’s baby and was always telling him that they should take their relationship to the next level.

“Sean’s telling her that he has no interest in starting a new family, but she’s determined to have a child with him,” a source was saying for the tabs at the time, as we also informed you.

The age difference (she’s 26, he’s 50) may have also played a part in the breakup.