Linde has recently been added to the list of hundreds of western companies suspected of paying bribes to the former government of Iraqi dictator Saddam Hussein.
A united nation report found that more than 2,200 companies from some 40 countries are suspected of secretly acting together with Saddam Hussein's regime to cheat the oil-for-food programme in Iraq of $1.8bn.
The weekly magazine Focus said German prosecutors were seeking evidence of payments from when Linde sought business under the United Nation Oil-for-Food programme. Such payments could be illegal under German foreign-trade law.
Christian Schmidt-Sommerfeld, a Munich prosecutor said in a report for the weekly focus that Linde's offices in Munich were searched in November as part of the investigation, but refused to divulge any other details.
Uwe Wolfinger, head of external communications at Linde, told The Associated Press that the company is cooperating with authorities to the fullest extent.
The Oil-for-Food Programme was designed to help poor Iraqis during UN sanctions from 1996 to 2003. Iraq exported oil and was supposed to purchase food and medicine, though many of its purchases circumvented the sanctions.