Police in Newburyport, Massachusetts, confirm the lockdown at Newburyport High School has lifted.
Police say officials at the high school received an unspecified threat early Tuesday morning against staff, faculty and students.
Officials say the email threats were unfounded and the building was deemed safe.
The latest news from around the state
One person is in custody for having a knife, but say it is unrelated to the threat.
Police are continuing to investigate the anonymous threat.