U.S. authorities said Wednesday they had arrested a suspect who is believed to have opened fire at a high school in Florida — an incident that one official said had caused “numerous fatalities.”

Senator Bill Nelson of Florida said there were “multiple fatalities,” while the sheriff’s office said there were “at least 14 victims.” Meanwhile, Margate Fire Rescue, the local fire brigade, told broadcaster CBS Miami that as many as 50 people had been injured.

The Broward County Sheriff’s Office tweeted Wednesday afternoon that “so far we have at least 14 victims.” The tweet added: “Victims have been and continue to be transported to Broward Health Medical Center and Broward Health North hospital.”

The sheriff’s statement didn’t elaborate on the victims or their injuries.

In this frame grab from video provided by WPLG-TV, students from the Marjory Stoneman Douglas High School in Parkland, Fla., evacuate the school following a shooting, Wednesday, Feb. 14, 2018 (AP Photo)

Marjory Stoneman Douglas High School had been placed on a “code red” lockdown, the spokeswoman said. Local FOX-10 TV reported that five people were seen being treated by paramedics.

Students are being evacuated to a nearby school. TV footage showed SWAT teams entering the campus and rescue workers loading people into ambulances.

Margate Fire Rescue has deemed this a mass casualty incident, which means at least 20 people have been injured, according to local broadcaster WSVN.