Criminal investigation bureau
It's actually the Division of Criminal Investigation, which is a part of the state Department of Justice. Within DCI there are several bureaus and units. One houses state narcotics agents, another the state fire marshals, one covers financial crimes including gambling and another one handles corruption by public officials. It includes an Investigative Services Bureau that assists local police and sheriffs with difficult crimes or where a state-wide crime pattern appears.
These frequencies may also be available to the Division of Law Enforcement Services, which inlcudes the State Crime Lab. The state Blue Book at your library will give you some more details (page 455-47 in the 2005-2006 edition). There are not a lot of DCI agents; one reason the radio traffic is sparse.