AUGUSTA, Maine (AP) Maine’s independent senator wants the U.S. Centers for Disease Control and Prevention to provide more information about how it is monitoring variants of COVID-19.

Sen. Angus King and Republican Sen. Bill Cassidy of Louisiana said they sent a letter to CDC Director Rochelle Walensky last week asking for the information. They said the spread of variants throughout the U.S. is cause for concern and greater monitoring.

The senators said in a statement they want to know “answers from the CDC on steps being taken to track virus genomes for relevant mutations and assess any increased risk to the American public.”

Two coronavirus variants have been located in King’s home state of Maine. One originated in the United Kingdom and the other in South Africa.