LINCOLN, Neb. (AP) — The U.S. attorney’s office in Nebraska says it can’t determine whether state officials violated federal law in their efforts to obtain lethal injection drugs, so prosecutors have forwarded key documents to a watchdog agency for further review.

Prosecutors examined the documents at the request of the American Civil Liberties Union of Nebraska. Danielle Conrad, the group’s executive director, said Friday she was pleased that prosecutors took the matter seriously.

The documents obtained by the group show state officials tried to obtain lethal injection drugs after the U.S. Food and Drug Administration said they can’t be imported.

U.S. Attorney Deborah Gilg says in a letter that her office sent the documents to the FDA’s Office of the Inspector General, and will decide whether to take action based on that agency’s report.