The World Health Organization's cancer research agency says mobile phones are "possibly carcinogenic".
A review of evidence suggests an increased risk of a malignant type of brain cancer cannot be ruled out. However, any link is not certain - they concluded that it was "not clearly established that it does cause cancer in humans". A cancer charity said the evidence was too weak to draw strong conclusions from.
A group of 31 experts has been meeting in Lyon, France, to review human evidence coming from epidemiological studies. They said they looked at all relevant human studies of people using mobile phones and exposure to electromagnetic fields in their workplace.
The WHO's International Agency for Research on Cancer (IARC) can give mobile phones one of five scientific labels: carcinogenic, probably carcinogenic, possibly carcinogenic, not classifiable or not carcinogenic.
It concluded that mobiles should be rated as "possibly carcinogenic" because of a possible link with a type of brain cancer - glioma.