Updated

Three Baltimore firefighters died and a fourth was critically injured on Monday after responding to a blaze in a vacant home, officials said, as Maryland Gov. Larry Hogan called the tragedy "our worst nightmare." 

Hogan announced on Monday evening that he had ordered flags be lowered to half-staff in honor of the three Baltimore City firefighters who died in the line of duty earlier that day. 

"Our hearts are broke for the entire Baltimore City Fire Department," he said, in part. "Each and every day, our firefighters and first responders answer the call and are ready to run into danger – this is our worst nightmare."

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Firefighters responded to a fire at a home on South Sticker Street around 6 a.m., the Baltimore City Fire Department tweeted

Baltimore City Fire Department Chief Niles R. Ford tweeted that firefighters were responding to a burning three-story rowhouse when a partial collapse trapped four members inside.

One firefighter was immediately pulled from the vacant house, the chief said. Crews cleared piles of debris and found two other trapped firefighters within an hour of the fire, he said.

By just before 9 a.m. local time, three firefighters were taken to an area hospital in serious condition. Firefighters had been working to rescue a fourth member who was trapped inside the home, the department said.

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The Baltimore Fire Department identified the firefighters who lost their lives as Lt. Paul Butrim, Firefighter Kelsey Sadler, and Firefighter Kenny Lacayo. Firefighter John McMaster remains in the hospital in critical but stable condition, the department said.

Fox News' Tyler O'Neil and The Associated Press contributed to this report.