A gas explosion early Monday morning in Jerusalem killed two parents and their 3-year-old child, and left 11 others injured, one of them critically.

The blast occurred on the third floor of the four-story building on Shabtai HaNegbi Street, in the Gilo neighborhood in the southern part of the city, causing it to collapse partially.

The explosion, which was heard miles away, was the result of a leak.

The toddler was pulled from the rubble, and paramedics worked unsuccessfully to resuscitate the unconscious child. Paramedics initially feared that another child was trapped.

After 3 a.m., a 20-year-old survivor with serious burns was pulled from the rubble. Emergency personnel later estimated that there were no more residents trapped in the building.

Victims of the blast were transported to the Shaare Zedek Medical Center and Hadassah Ein Kerem Hospital in Jerusalem.

Early Monday morning, police arrested a gas technician who had done work on the building Sunday evening, on the suspicion that he had been negligent and could have prevented the blast.

A spokesman for the gas company, Supergas, said the technician had been called twice to the building on Sunday, and had turned off the gas. Residents of the building said he assured them that the problem was taken care of, and that when they complained that they still smelled gas, he reassured them that the odor would go away.

“It is hard to know the source of the blast,” Shachar Ayalon, head of Israel’s firefighting services, told Ynet. “We will try to recreate the event and come to a conclusion on how this happened. The neighbors said they called a gas technician. It is unclear to use what exactly he did, but there is no doubt we are looking at negligence.”

“This is a real tragedy,” said Jerusalem Mayor Nir Barkat, who was at the scene in the early hours of the morning.

He said that the first priority was to make sure no one else was left inside the building, and that all the families would have a place to sleep.