Volkswagen has quietly purchased a significant number of shares in Navistar International Corporation, parent company of International Truck and Engine, during the month of July, according to reports from various international financial news sources.

Volkswagen has been a major shareholder in International since purchasing a $250 million stake in the Lisle, Illinois, company in September of last year and the two companies have collaborated on diesel engine technology for commercial trucks for over a decade.

According to a report in the financial journal Week Herald, Volkswagen acquired 43,501 shares of International stock on Monday, July 17, at an average price of $29.25 per share, for a total transaction of $1.272 million. That transaction was followed closely by four additional Navistar stock purchases by Volkswagen in July, ultimately netting the German car and truck manufacturer an additional 341,663 shares in the company for approximately $10 million. All told, Volkswagen invested approximately $11.26 million in Navistar International stock last month.

According to additional reporting by the United Kingdom’s Press Herald, as of July 21, 2017, Volkswagen owns approximately 16.4 million shares of Navistar International stock, which is approximately 17% of the company’s overall market capitalization.