BLACKSBURG, Va. -

Blacksburg police say the suspicious looking containers discovered Wednesday morning at Blacksburg High School are used to test concrete.

Samples are tested in the containers to make sure the concrete has been mixed correctly. Authorities believe they fell off of a work vehicle.

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Police say Blacksburg High School is safe after at least two suspicious containers were reported on Wednesday morning.

Blacksburg police and several law enforcement agencies have declared and "all clear" in the area across from the school.

A police spokesman said someone reported containers wrapped up with tape, placed across the street from the school's main entrance. They got the call around 8:20 a.m.

Odell said State police X-rayed the objects, took photos and determined they were not dangerous.

Investigators will follow up and determine if whoever placed the containers on the sidewalk did so intentionally to create a scare.