Package with 'homemade explosive substance' discovered near Arizona State Capitol

A package that officials said contained two vials of a "homemade explosive substance" was discovered near the Arizona State Capitol in downtown Phoenix on Monday.

The Arizona Department of Safety said multiple buildings were evacuated on the Capitol Mall, including the State Courts Building, which houses the Arizona Supreme Court and Court of Appeals.

"The State Courts Building remains closed as additional sweeps are taking place," the agency said. "Once that process has been completed, the package will be removed for further investigation and subsequent disposal."

An investigation into the incident is ongoing.

This is a developing story. Please check back for updates.

ABC News' Jenna Harrison contributed to this report.