The impact area where a medical transportation plane crashed in Philadelphia was notably “expansive,” U.S. Transportation Secretary Sean Duffy said Monday after viewing the site with investigators and city officials.

A plane crashed into a residential neighborhood near the Roosevelt Mall Friday evening causing an explosion, setting many homes ablaze and sending debris flying.

The six people on board the Mexico-bound medical jet include a girl who had received life-saving treatment at a Philly children's hospital, her mother, a pilot, copilot, doctor and paramedic.