Authorities remained at the Sheldon Clark High School in Martin County early Friday afternoon, but Kentucky State Police said the school is safe.
"I don't think there is any imminent danger, nor was there any at the beginning to my understanding," said Trooper Shaun Little, a spokesman with the Pikeville Kentucky State Police post. Little indicated that no one was trying to enter the school.
"They were in a lockdown due to something that occurred within the school itself," he said.
Little said the Martin County Sheriff's Department went to the school Friday morning, and Pikeville post sent a trooper to assist.
The Martin County Public Schools said the school went on "precautionary lockdown" about 10:30 a.m., but no official reason was immediately given.
Little said at 1:30 p.m. that he didn't know whether the lockdown was still in effect.
The high school and its students are "secure," according the Martin County Schools central office.