The three firms are supected of padding invoices submitted to the company building Berlin's third airport (BER) which has been plagued by cost overruns and delays, the Bild am Sonntag newspaper reported Sunday.
Lawyers for the airport consortium called the rate at which the additional bills were paid "unparallelled and suspicious," according to report.
Citing internal documents, the newspaper said that the anti-corruption unit of the consortium responsible for the third airport had launched an investigation into large payments to the three companies approved by top airport executives.
A spokesman for Siemens declined to comment on the report but said that the company had introduced broad internal review practices in recent years.
"We cannot completely rule out wrongdoing by individuals but if there are indications that the law and internal guidelines were violated we will decisively investigate this in cooperation with the relevant authorities," the unnamed spokesman told the dpa news agency.
Bosch and T-Systems declined to comment on the report but Bild quoted an airport consortium spokesman as saying that "all payments made since the start of the project will be subject to another overall review.”
Germany's new BER international hub was supposed to open in 2011 but is now billions of euros over budget and years behind schedule.
Billions down the drain
Estimates of the current cost hover around 5.4 billion euros ($5.9 billion) with millions spent each month in maintenance costs alone.
A symbol of mismanagement and waste, the unfinished terminals have tarnished Germany's reputation for efficiency and technical competence.
Serious techncial flaws in the airport's fire suppression system has been one of the largest hurdles in finishing the airport, slated to open later next year.
But even that date is in doubt after the firm handling major work declared bankruptcy earlier this month.
jar/bw (AFP, dpa)