SWAT and police are seen in Coral Springs, Florida, US, February 14, 2018. Image obtained from social media/Twitter/@Grumpyhaus

At least three people died and 50 were wounded when a gunman opened fire at a Florida high school on Wednesday, local media reported, with dozens of police and emergency officials surrounding the building while students fled.

Marjory Stoneman Douglas High School in Parkland ? about 72 kilometres (45 miles) north of Miami ? had been placed on a ?code red? lockdown but had no information on victims, a spokeswoman for the county sheriff?s office said.

SWAT and police are seen in Coral Springs, Florida, US, February 14, 2018. Image obtained from social media/Twitter/@Grumpyhaus

The sheriff?s office said on Twitter that the shooter was still at large.

Florida?s WSVN-TV reported at least 20 people were injured.

Live television showed dozens of students running and walking away from the school, weaving their way between large numbers of emergency vehicles including police cars, ambulances, and fire trucks.

Image Courtesy: CNN/Screenshot

Others, in the television images, were being led out of the school by heavily-armed police officers and an armoured vehicle filled with a SWAT team arriving at the scene.

One injured victim was seen being placed into an ambulance on a stretcher.

Local FOX-10 TV reported that five people were seen being treated by paramedics.