A study released Friday found an increased risk of certain cancers in animals exposed to cell phone radiation, a conclusion that could reignite concerns over the safety of the widely used devices. However, some scientists expressed serious concerns about the study, saying its results contain several inconsistencies. Even officials at the National Toxicology Program, which conducted the research, said the report fails to provide the clear answers many seek. Researchers found small increases in rare cancers in the brains and hearts of male rats exposed to nearly constant, high doses of radiation from cell phones, compared to rats that weren't exposed. There was no increase in cancer among exposed female rats, according to the study, which represent "partial findings" of a larger project. The rats were exposed to "whole body" cell phone radiation for a total of nine hours a day for two years. Between 2.2% to 3.3% developed malignant gliomas, a type of brain tumor. Between 1.1% and 6.6%