RALEIGH, N.C. (WNCN) — Broughton High School in Raleigh was put on a code yellow community lockdown on Tuesday morning due to a “threat,” according to a letter from Principal Elena Ashburn.

According to the letter sent to Broughton parents, the campus went on lockdown at approximately 8:35 a.m. “because of what has been deemed a threat to our campus.”

Ashburn said that the school had all exterior doors locked and no one was allowed to enter or exit the building as part of the lockdown.

“We immediately notified law enforcement who arrived very quickly and are currently conducting an investigation, along with ensuring safety for our school,” the letter said.

Students were told to remain in their first period class until school leaders gave clearance to lift the lockdown, which happened around 10:10 a.m., according to a follow-up letter from Ashburn.

Raleigh police told CBS 17 that a “robo-type call” was made to the school at 8:11 a.m. and included specific threats. The school then went on lockdown and officers, along with K-9 units, responded to the school and began a search.

“After a thorough investigation, the Raleigh Police Department has determined that there is no credible threat to our campus, as the threat was tracked to have originated out of state. In addition, an area of the campus specified in the threat was swept with police dogs and declared to be safe,” Ashburn said.

Police said the number that called the school appeared to be the same number used to make other threats at schools around the country.

Broughton will have additional law enforcement officers on campus for the remainder of the day, but the school is now back to its regular schedule.