Classes at DuVal High School in Lanham, Md., resumed for the day shortly after a lockdown was lifted after about 90 minutes Wednesday.
Prince George's County Schools tweeted at 12:20 p.m. that the lockdown had been lifted. The incident was a false alarm, school officials said.
The incident began as a "non-specific threat," News4's Pat Collins reports. The principal of DuVal heard that someone had brought a gun or other weapon to school. School officials then locked down the school and called the police, who brought in a K-9 unit and searched the school.
The school district said all students and staff were safe at the time they announced the lockdown on Twitter at approximately 11:45 a.m.
A letter will be sent home with students.
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