Update 4.31pm: A firefighter has been injured escaping from a blaze through a first floor window of a house.
The officer, in his 20s and with almost two years' service with Kildare Fire Service, was tackling a blaze in Canal Walk, Athy, when the incident happened.
The fire, which started downstairs in the terraced house, was believed to have been extinguished when it unexpectedly reignited, forcing the firefighter to flee from the upper floor.
He suffered non-life-threatening injuries when he forced open an upstairs window and jumped to the ground.
Locals initially raised concerns of a gas explosion in the property but that was ruled out by fire chiefs.
Celina Barrett, Chief Fire Officer with Kildare Fire Service, said: "The guys were working to extinguish the fire inside the building when one of our firefighters was injured. Thankfully his injuries are not life-threatening. We are hoping that he will make a full recovery.
"There was no gas explosion.
"The fire did not behave as we expected."
It is understood the firefighters and the incident commander believed the blaze had been extinguished and were beginning to ventilate the property when it reignited upstairs.
One person was in the house when the fire initially started at about 10am, Kildare Fire Service said.
They escaped unharmed.
Garda scenes of crime officers have been called in to establish how the blaze started and to see if there is any explanation for the fire reigniting.
Fire crews from Athy and from Stradbally in Co Laois attended the scene.
Earlier: Two firefighters have been hospitalised with non-life-threatning injuries following an incident at a house in Kildare.
Emergency services were alerted to an incident at a home in Canal Walk, Athy, at 10:45am this morning.
It is not clear if the house was occupied at the time, but none of its residents were injured.
Hoping that our injured Kildare FS colleagues will make a full recovery after a call in #Athy with @LaoisFireRescue photo @emergencytimes pic.twitter.com/CeP1Lc7Kqm— Dublin Fire Brigade (@DubFireBrigade) June 28, 2017
The surrounding homes were evacuated as a precaution.
The cause of the incident has not yet been established but there have been suggestions locally it was related to a gas leak.
Local labour councillor Mark Wall attended to the scene and said thankfully the people living in the house were removed.
— Dublin Fire Brigade (@DubFireBrigade) June 28, 2017
My thoughts and that of all Athy are with the young fireman injured in the incident this morning.
You are in our prayers.— Thomas Redmond (@Thomas_Redmond) June 28, 2017
"People on the ground where the fire took place are saying it was some type of explosion.
"There has been bad smoke damage and it may have entered a neighbouring house.
"Our thoughts are with those who thankfully have been taken from the house, and also thoughts with the fireman who has been removed as I understand to the hospital," he said.