The materials of the criminal case contain information that an official of Rīga Hospital No. 1 may have abused his or her position by rigging procurement contracts, and that a contractor performing construction work may have falsified documents, KNAB said in a release.
"During twelve searches, a large amount of documents and data devices were removed, which could have the role of evidence in criminal proceedings," KNAB said.
Three persons are currently in detention.
"We emphasize that the elimination of corrupt criminal offenses in public procurements by state and local government institutions is one of the priorities of the KNAB," the bureau said.
"Criminal investigation is at an early stage. KNAB will provide more detailed information on the particular criminal proceedings as soon as possible without compromising the interests of the investigation," it added, along with a reminder that all are innocent until proven guilty under the law.
According to its website, Riga Hospital No. 1 is the oldest hospital in Latvia, founded in 1803 under the personal edict of Tsar Alexander I.
In 2011 at the initiative of the Riga City council another renewal of the hospital was started with more than 30 million euros invested over five years in the renovation project.