Los Angeles ? Federal regulators are expanding their investigation into children’s jewelry that contains the toxic metal cadmium, promising that a recall announced Monday of “Best Friends” charm bracelets will not be the last.

“More recalls are in the works,” U.S. Consumer Product Safety Commission spokesman Scott Wolfson said.

Those recalls would be the result of voluntary testing by companies, some of which have found troubling levels of cadmium and then reported those results to the agency, Wolfson said. He would not say how many products are under scrutiny.

In addition, in recent weeks agency inspectors working at 10 of the nation’s largest ports have screened imports of jewelry for cadmium. In one instance, a shipment of Chinese jewelry was turned away.

Word of expanded federal efforts came as the consumer safety agency announced the voluntary recall of about 19,000 “Best Friends” charm bracelet sets made in China and sold exclusively at the jewelry and accessories store Claire’s, which has more than 3,000 outlets in North America and Europe.

Medical research shows that cadmium in high levels is a known carcinogen and can harm kidneys and bones.