Police are holding one person in custody after a gunman opened fire at a Georgia high school, and multiple casualties have been reported, local authorities say.

Details on the number or their conditions are not available at this time, said Barrow County Sheriff’s Office in a statement.

The school, Apalachee High School in Winder in Barrow County, was put on lockdown on Wednesday morning as the students were escorted outdoors to a nearby designated safe zone.

Dozens of police officers gathered at the school, where approximately 1,900 students are enrolled.

Footage from a helicopter at the scene showed emergency responders treating multiple people, according to a local Fox News affiliate.

After the school was cleared, students were released to their families, some picked up by their parents directly, others sent home by school bus.

The Georgia Bureau of Investigation said it was assisting local officers and advised “anyone near the area to stay clear while authorities investigate”.

The White House press office said President Joe Biden has been briefed on the incident and was coordinating with local officials.