A couple were found dead at their home after their nine-year-old daughter dialled 999 when she could not wake them, police have said.
The girl's mother and father, thought to be in their 30s, were pronounced dead by paramedics called to a house in Frankley, Birmingham, at about 10am on Friday.
Speaking outside the property in Miranda Close, Detective Chief Inspector Wayne Jones said officers had found no sign of major trauma on the bodies and were treating the deaths as "unexplained".
Mr Jones said the man was found dead in the lounge of the property, while the woman was discovered near a mattress in a bedroom.
Although their deaths are not being treated as suspicious at this stage, the staffing and resources of a murder inquiry have been allocated to the investigation.
Mr Jones said: "We are looking at all options, but at the moment the deaths are being treated as unexplained and we are continuing with our inquiries. There are no obvious signs of injury."
The nine-year-old girl, who thought her parents were asleep, is being cared for by relatives and specially trained officers, Mr Jones said.
It is understood the youngster was taken to hospital for precautionary checks after the emergency services were called to the scene.
Mr Jones said detectives were examining whether the deaths may be linked to carbon monoxide poisoning, and had no information to suggest they could be drug-related.
The officer added: "There is no obvious sign of major trauma and we await the outcome of the post-mortem examinations to determine the cause of death. The property has been secured as forensics experts examine the scene for evidence."