PLYMOUTH, Minn. -- A high school in Plymouth was under a shelter-in-place Tuesday morning.

According to an alert on Armstrong High School's website, the shelter-in-place order was made "as an abundance of caution" and everyone is safe.

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School officials later said a situation on a school bus prompted the shelter-in-place, which was put in place at 8:40 a.m. and lifted at 10:15 a.m. 

According to the school, there was a report that an individual allegedly in possession of a gun may have boarded a bus. After looking into it, nothing out of the ordinary was discovered. 

There was also a similar report made at Cooper High School around the same time. Again, no weapon was found.