WASHINGTON — Two government studies that bombarded rats and mice with cellphone radiation found a weak link to some heart tumors.

But scientists and federal regulators say don’t worry – it is safe to use your device. They still do.

Previous studies of cellphone users had found little reason for concern, but the newest research took a closer look at the effects of super-high doses in animals to address some lingering questions that could not be tested on humans.

The rat study released Friday found a small increase in an unusual type of heart tumor in male rats, but there were no significant problems in female rats or in a separate study of mice. In particular, scientists could not find hard evidence for concern about brain tumors.

The lead author of the research, John Bucher of the National Institute of Environmental Health Sciences, is not changing his cellphone use or advising his family to.

“I am actually holding my cellphone up to my ear,” Dr. Otis Brawley, the American Cancer Society’s chief medical officer, said in an interview after reading the studies.

The findings about the rare nerve-tissue tumor discovered in the hearts of male rats do not translate directly into a concern for humans, Bucher stressed.