Matt Damon had to pull out of a charity fundraiser because of a "family emergency of a serious nature".

The 'Bourne Ultimatum' star was due to host an event for OneXOne - a charity which aims to improve the health and wellbeing of impoverished children around the world - in San Francisco but instead had to return to his home in Boston.

Representatives for the 39-year-old actor have revealed the emergency didn't involve any of his children with wife Luciana Bozan - Isabella, three, and 14-month-old Gia Zavala.

Charlize Theron is expected to attend the gala.

Meanwhile, Hollywood director Steven Soderbergh has praised Matt for his fantastic work ethic on new movie 'The Informant!'.

Soderbergh, who also directed Damon in 'Oceans Eleven', said: "It was such an odd story and it required a certain kind of performance

"In this case, having worked with him was a huge benefit because we had to move so quickly."