The Cave Creek Post Office resumed operations on Nov. 20 after briefly closing when a package leaked mercury.
Environmental officials cleared both buildings for re-occupancy and the locations were re-opened to employees and the public on Nov. 23.
U.S. Postal Services officials have said that all packages that were being held at the Arcadia Post Office have been returned to the Cave Creek location.
An independent environmental team conducted a rapid response investigation of the facilities. The assessment included visual inspection, real-time air monitoring and remediation and cleanup of materials that were contaminated by the mercury.
Industrial hygienists from the environmental team and the postal service worked together to view data and crosscheck the information with the federal guidelines and postal policy.