Police are responding to a shooting at Sandy Hook Elementary School in Newtown, in western Connecticut.
NBC4 New York reported that the shooter has died and the school principal was shot and children were seen leaving the school covered with blood, and that police were swarming the surrounding neighbourhood telling residents to go inside and stay in their homes. Ambulances were also on the scene.
Three people have been brought to nearby Danbury hospital, NBC4 reported, and police have blocked off streets nearby.
Police are now going room by room through the school, evacuating staff and students. Children were in classrooms for their morning meeting when the shooting began. Teachers rushed the kids to the corner of the rooms and locked the doors.
State police say Newtown police called them at about 9:40am local time about the reports.
The Newtown Bee posted a photo of a group of young students - some crying, others looking visibly frightened - being escorted by adults through a parking lot in a line, hands on each other's shoulders.
The school superintendent's office says the district has locked down schools as a preventive measure to ensure the safety of students and staff.
"Due to reports of a shooting as yet unconfirmed, the district is taking preventive measures by putting all schools in lockdown until we ensure the safety of all students and staff," Newton Public School District secretary of superintendent Kathy June said in a statement, ABC News reports.
The superintendent's secretary, Kathy June, says reports of a shooting are not confirmed.
State police spokesman Lt. Paul Vance says they have a number of personnel on the scene to assist.