Four children were injured, two critically, after a fire tore through a building in Washington Heights Wednesday night, police said.

First responders were called to the six-story apartment building on Audubon Avenue at around 11 p.m. Video from the Citizen App shows multiple FDNY ladders extended into the upper floors as firefighters worked to bring the blaze under control.

Police said a 29-year-old woman and two 9-year-old girls were taken to NewYork-Presbyterian/Columbia hospital in stable condition, suffering from smoke inhalation.

A 2-year-old boy was also taken to NewYork-Presbyterian/Columbia hospital in critical condition, officials said, and a 1-year-old boy was taken to NewYork-Presbyterian/Weill Cornell Medical Center, also in critical condition.

Police said it’s unclear if all the children were related.

The city fire marshal was still investigating Thursday morning to determine how the fire started.