At least 20 people – and with some reports saying up to 50 people – have been injured after a gunman opened fire at Marjory Stoneman Douglas High School in Florida, United States.

The shooter is still at large, according to the Broward County Sheriff‘s office. Police have confirmed he’s male, but have not yet released any further information.

[UPDATE: Police have now confirmed the shooter is in custody.]

Around 2:30pm a fire alarm went off, and then the shooting began, a student told CBS News. The school had had a drill earlier that day.

The student, Jeiella Dodoo, said she heard six gunshots. A friend told her that people were being loaded into ambulances. “That’s when we knew it was really real, there was an actual shooter on campus,” she said.

One student still in lockdown posted photos on Twitter, showing people huddled behind desks.

“My school is being shot up and I am locked inside,” he said. “I’m fucking scared right now.”

Aerial footage shows students being led out of the school with their hands up.

People are being asked to avoid the area. We’ll update the story as it develops.

Image: AP