The Consumer Product Safety Commission is investigating reports of severe rashes caused by two new lines of Pampers diapers.

The diapers, called Swaddlers and Cruisers, were introduced in March by Proctor & Gamble, which markets Pampers. The CPSC has received a few reports of rashes that resemble chemical burns from the diapers, which use the company’s Dry Max technology and are a change from previous product lines. More than 4,000 parents are blaming Dry Max for the rashes at a Facebook page calling for Proctor & Gamble to bring back diapers that use paper pulp instead, the Associated Press reports.

Proctor & Gamble denies that there is any evidence its diapers caused the skin problems.