Officials said Thursday that the death toll from an apartment building fire in the Bronx has reached 12, including an infant. Four others have been critically injured.

Here's Mayor de Blasio's news conference:

BREAKING: NYC Mayor de Blasio says at least 12 people are dead in massive apartment fire in the Bronx. "This will rank as one of the worst losses of life to a fire in many, many years." https://t.co/vCAyse6kD2pic.twitter.com/Ul5UhMOkni

— ABC News (@ABC) December 29, 2017

"This will rank as one of the worst losses of life to a fire in many, many years," de Blasio said.

"At this moment based on preliminary information, and again there will be more information coming in in the next few hours, but based on the information now," he added, "we're very sorry to report 12 New Yorkers are dead, including one child as young as 1 year old."

"There are four people who are critically injured who are fighting on their lives, other serious injuries as well," he reported.

De Blasio said that so far another 12 people had been rescued and will survive. Firefighters are searching the building for other survivors.

Officials are still investigating the cause of the fire.

UPDATE: "Unspeakable tragedy" says @NYCMayor as death toll rises to 12 from Bronx fire, including a baby. Blaze broke out at a five-story building. VIDEO shows firefighters working in frigid temps to rescue people. #Bronxfire@KSL5TV@KSLcom@kslnewsradiohttps://t.co/1CAdsyvHmjpic.twitter.com/ipo6Ca7fWk

— Ladd Egan (@laddegan) December 29, 2017