Following the December 2013 death of a temporary worker at an Amazon fulfillment center in New Jersey, the federal Occupational Safety & Health Administration has issued citations to five companies involved in staffing the warehouse, while also revealing that it is investigating another death at an Amazon facility in Pennsylvania.

According to OSHA, the New Jersey fatality occurred on Dec. 4, 2013, when a temp worker hired to sort items for shipping became trapped in the Avenel, NJ, warehouse’s conveyor system.

OSHA did not mention Amazon in its list of companies cited for serious violations, but did call out third-party logistics contractor Genco, which had been contracted to to direct the temporary employees from four different staffing agencies.

Genco was cited for not certifying that a hazard assessment of the facility had been conducted before assigning employees to work the conveyor system. OSHA deemed this a serious violation, saying the employer knew (or should have known) that there was a substantial probability that death or serious physical harm could result from a hazard.

In addition to Genco, four temp staffing firms were also cited for failure to perform a hazard assessment of the facility.

The five companies each face a penalty of $6,000. They also each have 15 business days from receipt of their citations to comply or contest the citations.

“Temporary staffing agencies and host employers are jointly responsible for the safety and health of temporary employees,” said Patricia Jones, director of OSHA’s Avenel Area Office in a statement. “These employers must assess the work site to ensure that workers are adequately protected from potential hazards. It is essential that employers protect all workers from job hazards-both temporary and permanent workers.”

In addition to the New Jersey fatality, OSHA revealed that it is investigating a separate fatality that occurred on June 1 at an Amazon Fulfillment Center in Carlisle, PA.

Amazon has rapidly been expanding its network of fulfillment centers in order to keep up with customer demand and improve delivery times. The company has been heavily criticized for the conditions at a number of these facilities. For example, in 2011, workers at a Pennsylvania warehouse needed help from the media in order to get the e-tailer to install air-conditioning units after more than a dozen employees passed out inside the poorly ventilated building.

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