(AP)-- All students at a Denver-area high school are safe after a report that a man with a rifle was seen near campus, police said Friday.
"We've pretty much searched the building," Thornton Police spokesman Matt Barnes said outside Thornton High School in the northern Denver suburbs. "We've not located anything."
Barnes said a second search was planned.
No injuries were reported and there were no reports of gunfire.
Students left the school in single file, holding hands and led by police. They boarded school buses, and an officer was posted in each bus.
Authorities took the students to a nearby bus park-and-ride lot and told parents to meet their children there.
The school has 2,000 students and 130 staff members. Friday was the last day of classes before summer vacation.
"I'm freaking out," said Michelle Copeland, who was outside the school awaiting word on her 16-year-old son, Timothy Romero, a sophomore. "My knees are shaking. What if it's an automatic gun? Any gun, it doesn't matter."
She said Timothy texted her from gym class saying the school was on lockdown and heavily armed police were inside.
Amy Irsik said she sped to the school, crying all the way, after her 17-year-old son David sent her a text saying the school was on lockdown after the report of an armed man. "I love you," the text ended.
Thornton High student Ezequiel Cordova said he left the building at the order of police as an automated message came over the public address system announcing a security problem.
Niejha Andersen, 14, said her 16-year-old sister Toni texted her from inside the school shortly before noon that she was hiding under her desk. Toni is a junior at the school while Niejha is home-schooled.
Police cars surrounded the school and armed officers were visible.
The incident rattled Thornton, a city of 122,000 just 20 miles north of Columbine High School in the southwest Denver suburbs. Law enforcement was criticized for not moving quickly enough after the 1999 attack there in which two teenagers killed 12 students and a teacher before killing themselves.
After Columbine, police across the country developed tactics that call for responding officers to aggressively rush into schools or other scenes to stop any suspected gunman.