"There is no reliable attribution of the origin of hackers", the ministry’s spokesperson said.
Bloomberg has reported, citing sources, that a potential link with Russia in this case was visible.
The Hamburg-based Mabanaft and Oiltanking Deutschland, daughter companies of the fuel distributor Marquard & Bahls, said they discovered on 29 January that their IT systems had been hit by hacks. Oiltanking Deutschland, a large German tank storage logistics company, said its terminals were operating with limited capacity and declared "force majeure".
The German Interior Ministry said that the attack on Mabanaft, which stores and distributes fuel, posed a risk to critical infrastructure. The federal information technology security agency is involved in the probe.
"The prosecutor's office has opened an investigation on suspicion of blackmail after a ransomware attack on Mabanaft GmbH & Co. KG and Oiltanking Deutschland GmbH", a spokesperson for the Hamburg public prosecutor's office told Sputnik on 3 February.