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.

Production of BPA has steadily increased since the 1990s. According to a report by Environment and Human Health Inc. of New Haven, Conn., the amount produced jumped from about 16 pounds per year in the early 1990s to nearly 2.3 billion pounds in 2007. It is used in the production of clear, hard polycarbonate plastics and epoxy resins, often found inside food cans.

"Any products we're manufacturing now is BPA-free," said Jacqueline Burmitz, a spokeswoman for Playtex Products. She said the company stopped manufacturing bottles with the chemical in the fall of 2008.

As with other companies, Playtex is labeling its products as BPA-free.

The Food and Drug Administration has tentatively concluded that FDA-approved products containing BPA that are currently on the market are safe, based on a review of research. However, the agency said it will continue to consider new research and information that becomes available.

Some studies have shown that animals exposed to BPA have experience adverse health effects, including breast and prostate cancer, decline in sperm counts, early sexual maturation of females and neurobehavioral problems, according to Environment and Human Health Inc.