CHICAGO (CBS) — Two people were arrested early Monday, after breaking into a school under construction in the Jefferson Park neighborhood, police said.

Officers responded to Prussing Elementary around 3:20 a.m., after an alarm went off in the building.

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Police discovered an open window at the school, and as officers were investigating, a person who tried to run out of the building ran directly into police.

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Officers brought in a K9 unit to search the building, and found a second suspect inside.

Authorities said they believe it’s the second time the pair has broken into the school.

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Construction on a new annex at Prussing Elementary began in February. The project also includes renovations at the main school building. Work should be completed by the fall.