VERNON, Conn. (AP) — Investigators are trying to determine what caused a house to explode in Connecticut, injuring seven people, including four children, and sending debris flying.

Police, fire and rescue crews responded to the home in Vernon Thursday afternoon.

Three of the victims were outside when they arrived, while four more remained trapped in the rubble. Crews dug through what was left of the house to pull them to safety.

Four children were among the victims. Police say a 7-year-old boy appeared to suffer the most serious injuries.

The force of the blast blew the front door of the home across the street into a neighbor's yard. Glass and other debris littered the roadway.

Connecticut State Police troopers and K-9 teams assisted Vernon police and fire.