(Reuters) - Customers suing Sears, Roebuck and Co over alleged mold defects in their Kenmore-brand washing machines can bring their claims as a class action, a federal appeals court ruled on Tuesday. The 7th U.S. Circuit Court of Appeals, in Chicago, found that customers who sued over alleged mold buildup in the machines had enough in common to band together and pursue their claims collectively. "It is more efficient for the question whether the washing machines were defective - the question common to all class members - to be resolved in a single proceeding than for it to be litigated separately in hundreds of different trials," Judge Richard Posner wrote for a unanimous three-judge panel. Customers in six states who purchased Sears' Kenmore-brand washing machines after 2001 sued the company in federal court in 2006. One group of consumers claimed that the front-loading machines, with low water level and low water temperature, did not clean themselves adequately. The result was a buildup of mold in the drum that emitted a bad odor, the owners claimed. A second group of consumers said a defect in the control unit caused the machines to suddenly stop mid-cycle. Sears argued that the customers claiming mold problems could not sue together because the machines' manufacturer, Whirlpool Corp , had made a number of design modifications that undermined the similarity of individual owners' experiences. The trial judge agreed, refusing to certify the class on the mold claims. But the 7th Circuit reversed that ruling on Tuesday. "Sears does not contend that any of Whirlpool's design changes eliminated the odor problem but only that they reduced its incidence or gravity," Posner wrote. If the design changes greatly reduced the amount of mold buildup, the lower-court could then break the class into smaller groups, he added. Posner noted a decision by the 6th Circuit granting class status to a group of Ohio consumers who sued Whirlpool over similar mold claims. In the same opinion on Tuesday, the 7th Circuit panel also upheld the lower-court judge's decision to allow the customers alleging control-panel defects to proceed as a class. Sears declined to comment on the litigation, and Whirlpool did not immediately respond to a request for comment. Jonathan Selbin, a lawyer for the consumers, welcomed the decision. "It's a reaffirmation from a very influential court that when a company sells a defective product to thousands of consumers, the doors to the courthouse remain open because they can band together in a class and level the playing field," Selbin said. The case is Butler et al v. Sears, Roebuck and Co, 7th U.S. Circuit Court of Appeal, Nos. 11-8029, 12-8030.