Santa Fe police put Capital High School on lockdown Wednesday while they investigated a report that someone brought a gun to school.
Officers determined the threat was a hoax, police said in a news release.
During the lockdown, the school of around 1,400 students locked its doors and told students and staff to stay where they were.
Around 9:15 a.m., the school directed students and staff to shelter in place, which meant nobody was allowed to leave the building, Santa Fe Public Schools Superintendent Veronica García said.
After briefly returning to normalcy, the district detected a second threat on Instagram and called for a second shelter in place that lasted until early afternoon. García also said nearby Nina Otero Community School and César Chávez Elementary School were told to shelter in place.
The district tweeted around 1:15 p.m. that all three schools were no longer sheltering in place after police determined the area was safe.
Police said the incident remains under investigation.