WATERBURY, Vt. (NEXSTAR) — State police say three Vermont state troopers who are accused of being involved in a scheme to create fraudulent COVID-19 vaccination cards have resigned.

Troopers Shawn Sommers and Raymond Witkowski resigned on Aug. 10. Trooper David Pfindel resigned on Sept. 3.

State police said Tuesday that the three troopers are suspected of having varying roles in the making of fraudulent vaccination cards. A fellow trooper told supervisors about the alleged scheme, which may be a violation of federal law, police say.

“The accusations in this case involve an extraordinary level of misconduct — a criminal violation of the law — and I could not be more upset and disappointed,” said Col. Matthew T. Birmingham, director of the Vermont State Police. “If these allegations are proved to be true, it is reprehensible that state troopers would manipulate vaccination cards in the midst of a pandemic, when being vaccinated is one of the most important steps anyone can take to keep their community safe from COVID-19.”

An email seeking comment from the Vermont Troopers Association was not immediately returned on Tuesday.

“I’m embarrassed that this situation has occurred and know that it has tarnished the reputation of the Vermont State Police,” Birmingham continued. “That said, the alleged criminal conduct from these troopers does not represent the values and actions of the dedicated men and women of the Vermont State Police.”

Federal authorities are investigating the allegations.

In August, U.S. Customs and Border Protection revealed that officers at the port of Memphis seize hundreds of counterfeit COVID-19 vaccination cards every night.

The FBI has warned that buying, selling or using a counterfeit COVID-19 vaccination card is a crime and could result in a fine and up to five years in prison.

The Associated Press contributed to this report.