Federal investigators cited five companies for "serious" labor violations in the death of a worker at an Amazon.com warehouse in New Jersey but brought no action against the online retailer itself.
Ronald Smith, a temporary employee, was crushed in a conveyor system in December while sorting packages and later died from his injuries, the Occupational Safety and Health Administration said in a statement.
The agency said four temporary staffing agencies and the contractor responsible for operating the facility did not properly assess the risks to employees.
"Temporary staffing agencies and host employers are jointly responsible for the safety and health of temporary employees," Patricia Jones, director of OSHA's Avenel Area Office, said in the statement. "These employers must assess the work site to ensure that workers are adequately protected from potential hazards."
Labor investigators are also looking into a death that occurred earlier this month at an Amazon warehouse in Pennsylvania.
In response, the Seattle company said in a statement that "any accident that occurs in a facility is one too many and we take these matters seriously."
The online retailer has been targeted in the past by some labor activists for its treatment of employees. Hundreds of workers at warehouses in Germany reportedly walked off the job in April to protest for higher pay.
Amazon.com has been swiftly expanding its warehouse network around the country to get items to customers' doors more quickly. In California, the company has centers open in San Bernardino, Patterson and Tracy. It plans to build another one in Moreno Valley.