Richmond (AP) – Virginia is ceasing the use of all Johnson & Johnson COVID-19 vaccines while the federal government investigates rare reports of potentially dangerous blood clots among recipients of the vaccine.

Virginia State Vaccination Coordinator Dr. Danny Avula said in a statement Tuesday morning that the state was halting use of the vaccine until the federal investigation is complete.

“This pause is reassuring in that it demonstrates that the systems that are in place to monitor vaccine safety are working,” Avula said.

Anyone in Virginia with an upcoming appointment for the Johnson & Johnson vaccine will be contacted to reschedule that appointment, according to Avula. Virginia’s vaccine rollout will continue with the other two authorized vaccines, developed by Pfizer and Moderna.

Federal officials said Tuesday they are investigating unusual clots in six women. More than 6.8 million doses of the J&J single-dose vaccine have been administered in the U.S., the vast majority with no or mild side effects.