Companies sued in Philadelphia over the deadly 2017 fire in London’s Grenfell Tower have taken the litigation to federal court, where a new fight is shaping up over what plaintiffs claim is an effort by defendants to “sneak a peek” at their strategy.

Last month, Arconic, Celotex and Whirlpool removed the high-profile litigation from the Philadelphia Court of Common Pleas, where it was initially filed, to the U.S. District Court for the Eastern District of Pennsylvania. The litigation, which is said to be one of the largest products liability lawsuits in Pennsylvania history, stems from the June 2017 fire that engulfed the 24-story building in the North Kensington section of West London and left 72 dead, as well as 70 injured. The lawsuit brought claims on behalf of 177 survivors and 69 families of the deceased.