WASHINGTON -- Health secretary Robert F. Kennedy Jr. warned that children in the U.S. are being diagnosed with autism at an “alarming rate,” promising on Wednesday to conduct exhaustive studies to identify any environmental factors that may cause the developmental disorder.

For years, Robert F. Kennedy Jr. has raised questions about vaccine safety. Now, as the Secretary of Health and Human Services, Kennedy oversees the government’s key health agencies, including the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH).