Oak Forest police said they responded to the 5100-block of 160th Street for a report of a fire around 8 p.m.
A neighbor told ABC7 around 8 p.m. he heard and felt an explosion.
"I was sitting in my bedroom and heard a loud boom. It literally shook the building," Reggie Odell said.
When he went outside, he saw two spent dynamite canisters and massive damage to the building, including blown out windows and insulation all over the place.
"There was a stick of dynamite in the yard," he said.
Police said two people, a man and a woman, were injured and taken to Christ Hospital for treatment. They did not comment on their condition, though witnesses said they walked out of their home covered in blood.
No one else was injured.
Police also said the Bureau of Alcohol, Tobacco and Firearms is responding to the apartment complex to investigate.
It was not immediately clear if more people were involved in causing the explosion than the two injured, or whether the detonation was accidental or intentional..