(AP) — New York City Mayor Bill de Blasio says people are still missing after an explosion leveled two apartment buildings, killing two people and injuring 18 others.

De Blasio says: “There are a number of missing individuals.” He suggests some may have fled to safety and says the city is expending every effort to locate the people who are still unaccounted for.

The mayor urged worried relatives to call 311. A hotline was being set up.

The mayor says Con Edison is shutting down all gas mains going into the building.

He says a gas leak was reported to the utility 15 minutes before the explosion. The explosion occurred before the Con Edison team arrived.