More than 1,000 students were evacuated to the football field at a Philadelphia suburban high school on Tuesday after two men allegedly made threats and were seen on campus.

“We’re going through the school with K-9 bomb dogs,” Upper Merion Police Chief Ronald Fonock said.

The two men were taken into custody and being questioned.

"There were two non-student intruders in our building this morning. They were not armed. As an extra precaution, we decided to dismiss students for the day so police have full access to the school to search it," Superintendent Melissa Jamula said.

At least one of the men was a former student and the school acted on directions by police, Jamula said. She did not know if any students had been specifically threatened.

Classes were in session at the time and the school's approximately 1,100 students were evacuated, school officials said.

Upper Merion High School was locked down and students were evacuated to the football field.

The Associated Press contributed to this report.