Hilton Head Island High School had a brief lockdown Tuesday morning due to a safety issue, according to school officials. They declined to specify what prompted the lockdown, although Principal Amanda O'Nan said in an email to parents it was "due to information that was received."

School administrators and the deputy sheriff at the school searched and determined that the possible safety threat was unfounded, and school resumed normally.

The school was on what officials called a "modified lockdown" for about 20 minutes.

"A modified instruction allows instruction to continue in classes," O'Nan said.

If students needed to be in the halls for any reason they were accompanied by adults, school district spokesman Jim Foster said.

"We always take precautionary measures as needed as safety is a priority," O'Nan's email to parents said.