Veterans groups and some members of Congress say they’re outraged over revelations that Iraq and Afghanistan veterans with post-traumatic stress disorder (PTSD) are being recruited by the U.S. government for tests involving the anti-smoking drug Chantix, which has been linked to increased risk of suicide.

They’re calling for an immediate halt to the tests and an investigation, ABC News reported.

“Nearly 40 suicides and more than 400 incidents of suicidal behavior have been linked to Chantix, yet the [Veteran’s Administration] has chosen to continue the study and administer Chantix to veterans with PTSD,” said Congressman Bob Filner (D-CA). “The VA must immediately suspend this study until a comprehensive review of the safety of the protocol is conducted.”

“Our nation’s veterans are not guinea pigs,” said Paul Rieckhoff, executive director of Iraq and Afghanistan Veterans of America. “It is unacceptable for even one veteran to have been misled about the possible side effects of Chantix.”

The VA says the ABC News/Washington Post report about the study is “inaccurate and misleading.”

“In our PTSD and smoking cessation study, our research is to learn if it is easier to stop smoking when smoking cessation treatment is combined with PTSD therapy, or whether the two therapies are more effective if they are provided separately,” said a statement posted on the VA Web site, ABC News reported.

“In either case, patients are receiving treatment recommended by their own doctors using counselling with or without FDA approved medication that includes Varenicline (Chantix). Participation in this program is voluntary, and all participants are closely monitored clinically by mental health professionals who provide smoking cessation methods patients agree to use,” the statement said.