A state bureau of investigation (SBI) is a state-level detective agency in the United States. They are plainclothes agencies which usually investigate both criminal and civil cases involving the state and/or multiple jurisdictions. They also typically provide technical support to local agencies in the form of laboratory and/or record services, or to directly assist in the investigation of cases at the local agency's request.
An SBI is a state's equivalent to the Federal Bureau of Investigation, but can include investigative jurisdiction similar to other federal law enforcement agencies as well. The SBIs investigate all manner of cases assigned to them by their state's laws and usually report to their state's attorney general, or in some cases, directly to their state's governor.
SBIs can also exist either independently or within a state Department of Public Safety/Department of Justice (which is an umbrella agency coordinating and/or controlling the various state-level law enforcement agencies) or a state police force (which is a general law enforcement agency).