The Centers for Disease Control and Prevention (CDC) says the number of vaping-related injuries continues to increase, and has surpassed the previously reported estimate of 530, The Wall Street Journal reports.

Hundreds of new cases of injuries have been found through federal and state investigations in the past week, according to Anne Schuchat, Principal Deputy Director of the CDC. In testimony before the House on Tuesday, Schuchat said that half of all vaping-related injuries appeared in people 25 and younger. Three-fourths of patients are male.

She said most of the cases involved black-market products that include THC, the psychoactive ingredient in marijuana. She noted THC is not necessarily the cause of the injuries. “We don’t know if there’s a new, particularly risky product” that has touched off the outbreak, she said.