Government experts and lawmakers clashed at a hearing Tuesday over the safety of a chemical used in plastic baby bottles, as the science indicating health risks seemed not conclusive enough to meet the burden of proof required for a U.S. ban.

The chemical, bisphenol A, or BPA, makes plastic hard and shatterproof and helps prevent corrosion in cans. It is used in hundreds of consumer products, including plastic baby bottles, plastic food containers and soda cans.

The...