SAN FRANCISCO (AP) — A federal agency on Friday recalled toys sold at Walmart.com containing powerful magnetic balls that could pose a hazard to children if swallowed.

The Consumer Product Safety Commission said the balls, which are 5 millimeters (0.2 inches) in diameter, exceed federal standards for magnetic strength and could clump together to block parts of the digestive system when ingested.

The commission said no injuries had been reported from use of this particular product, called the Relax 5mm Science Kit. It contained 216 small, multicolored magnetic balls with what the CPSC called a “strong magnetic flux.”

The agency said that ingested magnets could attach to each other or other metal objects, potentially leading to perforations, twisting and/or blockage of the intestines, infection, blood poisoning and death.

The CPSC estimates that 2,400 magnet ingestions were treated in hospital emergency rooms between 2017 and 2021 and said the agency is aware of seven deaths related to the ingestion of hazardous magnets, including two outside of the U.S.

The magnet kit was sold at Walmart.com by Joybuy Marketplace Express, a unit of the Chinese e-commerce giant JD.com. As of mid-afternoon Eastern Time, the kits were no longer visible on Walmart.com.