Hartford, Conn. ? Connecticut’s attorney general announced Thursday that six companies have stopped manufacturing baby bottles containing Bisphenol-A, a chemical some studies suggest may be harmful to infants.

Attorneys general from Connecticut, Delaware and New Jersey sent letters last October to 11 companies, asking them to end their use of the chemical.

Avent America Inc., Disney First Years, Gerber, Dr. Brown, Playtex Products Inc. and Evenflo Co. are voluntarily complying with the request, said Connecticut Attorney General Richard Blumenthal.

The firms who’ve agreed to stop using the chemical manufacture the majority of baby bottles in the U.S., according to Blumenthal’s office. Avent America is a subsidiary of Philips Avent, while St. Louis-based Handicraft makes Dr. Brown’s baby bottles. Gerber is a subsidiary of Nestle USA.