Four people were found dead possibly from gas poisoning in Shanghai on Sunday morning. Police suggested a gas water heater could have caused the accident.

The victims are an old couple both in their 70s, their daughter-in-law and a 12-year-old granddaughter, a police spokesman said.

The old couple's son returned home on Sunday morning after a night shift, just to find the four in bed unconsciously. He immediately called the police.

Initial investigation showed the old water heater that lacked a forced ventilation system could have caused the accident.

(Xinhua News Agency December 7, 2008)