The Hague Fire Brigade said in a tweet that nine people in total were injured by the explosion that blew the facade off part of the three-story building in a residential neighborhood. Seven were taken to nearby hospitals for treatment. Their conditions were not immediately known.
The explosion scattered broken glass more than a block away and left a white van and a car badly damaged. As darkness fell, fire engine lights shined on exposed rooms where a sofa, table and chairs still could be seen on the third floor.
Sniffer dogs were brought in to aid the search. Rescue teams worked carefully because the building's extensive structural damage meant more sections might collapse. Fire Brigade spokesman John Kardol said it remained unclear what caused the gas explosion.