According to information by the daily, the KNAB is officially investigating Estonian businessman Ossinovski for bribery.
The Latvian authorities suspect the businessman of bribing former Latvian Railway head Ugis Magonis so that Ossinovski's company could sell four diesel trains to Latvian Railways. The deal was worth €8m.
According to Eesti Paevaleht, Magonis had at first asked for €800,000 but the figure was cut down during talks.
The Latvian anti-graft authority declined comment over the information and said that the investigation is ongoing.
The KNAB detained Ugis Magonis, chairman and president of state-owned Latvian Railways (Latvijas Dzelzcels) on August 7.
Magonis is suspected of accepting a bribe worth nearly €500,000 in connection with a tender for four diesel locomotives organized by the railway company's subsidiary, LDZ Ritosa Sastava Serviss, which was won by Estonian businessman Oleg Ossinovski's company Skinest.
Magonis was detained close to the Latvian-Estonian border with the money in his car.
In October Magonis was released from custody after his wife posted €400,000 in bail.