"It's amazing no one was killed," Phillipsburg mayor Stephen Ellis said.
The incident was reported around 5 p.m. in the unit block of Filmore Street.
Mayor Ellis says he knew something bad happen right away.
"I felt it. I was at my house. I had just left a Relay for Life event over at our high school and it shook the ground, which is about a mile away," Ellis said.
Amazingly, only two people were injured.
One victim, identified as 36-year-old Clay Metzger, suffered serious burns and remains in critical but stable condition at Lehigh Valley Hospital.
A neighbor, who didn't want to be identified, says it was obvious right away that Metzger was badly injured.
"The neighbor was spraying a hose onto him because his skin was coming off, it was so bad," the neighbor said.
The other person injured suffered a laceration to the face, but that victim is expected to fully recover.
Meanwhile, the question that lingers is how did this happen?
"We have specialists here from Elizabethtown Gas and we also have our detectives sifting through the rubble to find a cause," Ellis said.
Several neighbors reported to police there was an odor of gas in the neighborhood before the explosion occurred.
At least one of the neighbor homes may have to be demolished due to the damage.
Two dogs were injured in the blast. They are being treated for burns.