An explosion in Philadelphia today destroyed three homes and sent at least eight people to the hospital, at least one in critical condition.

The explosion happened in a row home in south Philadelphia at around 11 AM. Authorities say that the home was being renovated and the construction was taking place with a permit. A statement from the city says that although the specific circumstances are still being investigated, the cause of the explosion appears to have been natural gas. Witnesses claimed to notice a strong odor of gas immediately following the explosion.

The blast destroyed the home that was under construction and caused the two adjacent row homes to partially collapse. Eight people were sent to various Philadelphia area hospitals for treatment following the blast. One of the victims, the contractor who was working at the site of the blast, is reported to be in critical condition with severe burns. Among the other seven victims are a family of three, including a two-month-old baby who suffered burns.

According to a statement from the city, the situation was under control by 1 p.m., but several homes in the immediate vicinity remain evacuated. Authorities also said that everyone from the damaged homes appears to be accounted for, but that they would continue to sweep the wreckage with listening devices to make sure.