HOPKINTON (CBS) – A bullet was found inside Hopkinton High School Thursday morning.

Students were dismissed around 10 a.m. after the single round of ammunition was found in a common area, according to police.

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Police outside Hopkinton High School, February 1, 2018. (WBZ-TV)

Officers and the canine unit then swept though the complex.

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“After a thorough search of the school no weapons or additional ammunition were found,” police said in a statement Thursday afternoon.

“We have no reason to believe that a weapon was actually on school grounds.”

The middle school, which is next door to the high school, was put in a shelter in place for more than two hours.

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No other information is available at this point in the investigation.