The World Health Organization (WHO) says its 10-year study into a possible link between cancer and cell phone use yielded inconclusive results.

The Interphone study found no increase in risk of brain cancer with the use of cell phones but found that there were “suggestions” of increased risk at heightened levels of exposure.

The organization said “biases and error” prevented it from issuing any definitive conclusions and recommended further investigation into the effects of heavy, long-term use of cell phones.

“An increased risk of brain cancer is not established from the data from Interphone,” said WHO cancer research director Christopher Wild in a statement. “However, observations at the highest level of cumulative call time and the changing patterns of mobile phone use since the period studied by Interphone, particularly in young people, mean that further investigation of mobile phone use and brain cancer risk is merited.”

Because of concerns surrounding the rapid adoption of mobile phones by children, the Center for Research in Environmental Epidemiology in Spain is coordinating a new project to investigate the risk of brain tumors from mobile phone use in childhood and adolescence. The new project, called MobiKids, will be funded by the European Union.

CTIA vice president of public affairs John Walls reacted positively to the study.

“All cell phones sold in the U.S. must comply with the FCC’s radio frequency exposure standards, which are designed to include a substantial margin of safety for consumers,” Walls said in a statement. “Numerous experts and government health and safety organizations around the world have reviewed the existing database of studies and ongoing research and concluded that RF products meeting established safety guidelines pose no known health risk.”