A third-party monitor on Friday said that some of Mattel Inc.’s Southeast Asian factories were safe, although 40 percent of workers believed they were treated unfairly.

The International Center for Corporate Accountability audited Mattel factories in Thailand, Malaysia and Indonesia. The audit found that the facilities adhered to the toymaker’s principles guiding responsible manufacturing practices. El Segundo-based Mattel commissioned the audit, the third of its kind in an ongoing program to evaluate Mattel’s Southeast Asian operations.

Despite compliance with the principles, the center alerted Mattel that it should address a perception among some workers that the company isn’t fair and should consider suggestions to improve safety in areas around grinding machines. The center also recommended that Mattel clearly communicate residency requirements for single female employees and the voluntary nature of overtime.

Mattel said its management has already begun taking steps to clarify overtime issues and is responding to the other concerns touched on in the audit. The company contracts with the center, a non-profit affiliated with the Zicklin School of Business at Baruch College in New York, to perform regular audits of its factories and its suppliers’ operations. Mattel adopted the manufacturing principles in 1997 to ensure wages, working and living conditions are just.