U.S. Attorney Jerry Martin on Wednesday declined to provide more details to The Associated Press. Specifics of the investigation by the Environmental Crimes Section of the Justice Department have been filed under seal.

The prosecutor’s documents point out that the federal government can “seek criminal fines and imprisonment for knowing violations of the Lacey Act,” which bans the import of illegally harvested wildlife and plants.

The details are kept confidential so they don’t “compromise the criminal investigation,” according to court documents filed Tuesday in federal court in Nashville.

Agents last month raided Gibson factories and offices in Nashville and Memphis after seizing what they deem illegal ebony wood shipped to the guitar maker from India.

Gibson Chief Executive Officer Henry Juszkiewicz has denied wrongdoing and complained in multiple media appearances that the federal government has implicated Gibson without filing charges. A company spokesman did not immediately respond to a message seeking comment about the latest court filings.

Gibson has drawn the support of Republicans and tea party groups decrying the raids as examples of overzealous regulation and a threat to American jobs.

Gibson was the subject of a similar raid in 2009 after federal agents seized wood they alleged had been exported illegally from Madagascar. Proceedings in that case were put on hold last week pending the legal fight over the more recent seizure and because of the ongoing criminal investigation.

Gibson used Hamburg, Germany-based Theodor Nagel GmbH as its importer in both instances. A lawyer for Nagel did not immediately return a message seeking comment.