In the latest escalation of the legal battle between Anheuser-Busch InBev and MillerCoors, the Bud Light brewer is accusing its rival of stealing secret recipes for its beers, including Michelob Ultra and Bud Light.

MillerCoors, the U.S. subsidiary of Molson Coors, first filed a lawsuit against Anheuser-Busch in March after its rival aired a Super Bowl commercial that shamed Miller Lite and Coors Light for using corn syrup. In September, a federal judge issued a preliminary injunction against Anheuser-Busch, preventing the beer giant from using Bud Light packaging that says "no corn syrup." Anheuser-Busch is appealing the decision.

In a redacted counterclaim filed Thursday, the Bud Light brewer alleges that a former employee who now works at a MillerCoors brewery in Colorado was obtaining information from current Anheuser-Busch employees who were violating confidentiality agreements in the days before and after the Super Bowl. Some of his questions involved the use of corn syrup in the brewing process, Anheuser-Busch claims in the filing.

Senior executives from MillerCoors were asking for the information, and CEO Gavin Hattersley was included on email chains about the findings, the filing alleges.