A group of consumers have filed a proposed class-action lawsuit against Costco Wholesale Corporation, accusing the retailer of selling protein powder “tainted” with toxic heavy metals with no warning to consumers.

The lawsuit, filed on Tuesday in federal court in Washington state, names seven consumers as plaintiffs. They allege that Costco violated consumer protection and false advertising laws by selling and marketing Orgain Organic Protein Powder as “high quality, clean, and nutritious without disclosing the presence or risk of heavy metals, including lead, cadmium, and arsenic”.