Two people were injured in a blaze at an apartment complex Saturday in Logan Square on the Northwest Side.

Authorities responded about 2 a.m. to the 3200 block of West Fullerton Avenue, Chicago police said. There was a fire at an apartment on the second floor of the complex.

A man and woman were hospitalized in critical condition, police said. The man was taken to Stroger Hospital, and the woman was taken to Illinois Masonic Medical Center. No other injuries were reported.

The cause of the fire is under investigation, police said.