Final answer:
Both the host employer and the temporary employer are responsible for conducting an incident investigation on a multi-employer work-site.
Step-by-step explanation:
On a multi-employer work-site, both the host employer and the temporary employer share responsibility for conducting an incident investigation. According to OSHA, both entities are accountable for compliance with workplace health and safety requirements and ensuring worker safety and health. In cases of a violation, OSHA could hold both the host and temporary employers responsible.