Every federal department has an Inspector General and the employees are federal agents authorized to carry firearms and conduct raids. However contrary to the article, the OIG agents, like all other officers, have to get a judge to sign the warrant and approve it for no-knock service.

A few examples: NASA OIG: http://oig.nasa.gov/ USPS Postal Inspectors: https://postalinspectors.uspis.gov/ National Endowment for the Arts: http://www.nea.gov/about/OIG/Contents.html

All Inspectors General: http://www.ignet.gov/igs/homepage1.html