This story has been updated.
OSSINING, N.Y.-- Ossining High School's lockdown Wednesday, which was switched to a lockout later in the school day, was caused by an anonymous social media thread that was made late this morning, according to a letter sent out to parents by Superintendent Raymond Sanchez.
Sanchez said police have found no evidence of a credible threat and believe the building is secure. Police will remain in the building for the rest of the day, Sanchez said.
"These threats are a criminal offense and those responsible for such offenses will face appropriate discipline and potential legal action," Sanchez said. "The safety of our students and staff is our first priority. Our principal acted quickly and wisely to this threat.
"We thank you for your patience today and for understanding why sensitive information may not be immediately available during an incident."
Classes resumed but no one was being allowed to enter the building, police said. All other schools in the district resumed regular activities and dismissal times remained as scheduled.
Earlier in the morning, Sanchez and Principal Joshua Mandel sent a letter about comments made on social media that could be interpreted as a threat to the high school.
Police and the district determined that what the student wrote does not pose a threat to any student or building in the district, Sanchez and Mandel said.
In an unrelated incident, Roosevelt School in Ossining was evacuated this morning at 9:10 a.m. due to a strong odor in the building. District officials determined the smell to be the result of a faulty battery and students returned to the building at 9:40 a.m.
Click here to sign up for Daily Voice's free daily emails and news alerts.