A Turkish couple and their two young children were found dead Monday in their house in Esslingen, a town near southwestern Stuttgart city, in what authorities said was a case of suspected carbon monoxide poisoning.

Police were alerted on Monday by a relative who got no response when he rang and knocked on the door, and then saw two people lying on the floor through a window.

Fire officers found the bodies of a man and woman, both 29, their 3-year-old daughter and 4-year-old son inside.

Police spokesman Christian Woerne told Anadolu Agency that their initial investigation indicated that four members of the family died from accidental carbon monoxide exposure.

The poisonous gas has no smell or taste and its intake in large amounts may cause death.