SAN FRANCISCO — Apple Inc released on Friday an audit of its major suppliers, saying it found a number of violations including breaches in pay, benefits and environmental practices in plants in China.

The Cupertino, California-based company, notorious for keeping its supply chain a secret, also for the first time released a list of its major suppliers.

The company said it conducted 229 audits last year, representing an 80 percent increase over 2010.

Apple said it probed all levels of its supply chain, including final assembly and component suppliers.

The consumer device giant will grant access to an independent auditing team from the Fair Labor Association in an effort to overcome criticism regarding working conditions at factories in its supply chain.

"It's a level of transparency and independent oversight that is unmatched in our industry," Apple said in the audit report.

Apple said it found 6 active and 13 historical cases of underage labor at some component suppliers but said it did not find any underage workers at its final assembly suppliers.

The report titled "Supplier responsibility progress report" also said it asked suppliers to repay workers after it found 67 facilities had docked worker pay as a disciplinary measure.

Apple also terminated business with one supplier and was correcting the practices of another supplier. Both were repeat offenders, the report said.