AURORA, Colo. (AP) — Officials at the University of Colorado say they received two suspicious packages Monday at the Denver-area school.

The first package arrived early in the morning and was slipped under the door at a campus building while it was mostly empty. People were not allowed into the building until the threat was cleared. A spokeswoman says she does not know what the package was or who it came from.

The second package was addressed to a person in a separate building and came to the school's central mail facility.