Despite earlier reports that both children had died, officials have now indicated that may not be the case.
We are now awaiting further word from officials.
The fire happened along the 300 block of East Sheldon Street around 10 p.m. Thursday.
Arriving crews reported heavy fire coming from the upper floor of the rear of the two-story row home.
Two children rescued from 2nd floor of burning building in Olney last night,taken to hospital in critical condition. pic.twitter.com/j7yVLfX4Q4— Katherine Scott (@KScott6abc) November 4, 2016
Neighbors described the smoky conditions on the block.
"There was actually more smoke than flames," said Sammy Bautista. "It seemed like the fire was inside the house. No flames outside."
Officials say it took firefighters about 10 minutes to knock down the flames.
Shortly thereafter, they found and 11-month old and a 6-year-old inside.
Fire Commissioner Adam Thiel told Action News the heavy smoke in the building and the tight, constrained space made it difficult for firefighters to see.
"It's always difficult to locate people inside a burning building, despite what you see on television," said Thiel. "You can't see anything. There was a lot of smoke in there. I went inside. The smoke is all the way down to the floor. You can literally see nothing, so it's always a real challenge to locate people in these buildings. And ... our firefighters do an incredible job at it every day."
The cause of the fire is still under investigation, and it is not clear if the home had working smoke detectors.
We also don't know if any adults were inside the home at the time of the fire.