SAN FRANCISCO » AT&T has agreed to pay California authorities $23.3 million to settle allegations that it improperly disposed of hazardous waste over a nine-period.

California Attorney General Kamala Harris said Thursday that the telecommunications giant has also agreed to spend $28 million over the next five years to properly dispose of the waste, which includes batteries, electronic equipment and various gels and liquids. Harris said the investigation began in 2011 when inspectors with the Alameda County District Attorney’s office and the California Department of Toxic Substances Control examined trash bins outside some 235 AT&T warehouse and other facilities.

AT&T didn’t immediately respond to a request for comment.

Five other telecommunications’ companies have disclosed in financial filings with regulators that they are the targets of similar investigations.