No official cause of death is known for a San Gabriel woman and Tournament of Roses volunteer whose body was found in the trunk of her car in 2004, resulting in the arrest of an Alhambra man on suspicion of murder earlier this week, coroner’s officials said.

Richard Allan Munnecke, 71, was jailed Wednesday on suspicion of killing 59-year-old Donna Kelly, whose body was found by her daughter in April of 2004, sheriff’s officials said. She went missing about three weeks earlier.

Coroner’s medical examiners were unable to determined how Kelly died, largely because of the condition her body was discovered in, Los Angeles County Department of Coroner’s Assistant Chief of Operations Ed Winter said.

“(Cause of death) is undetermined after autopsy and toxicology. They don’t know why she died,” Winter said.

Investigators noted in their report that the cause of death was, “possibly masked by decomposition,” he added.

Detective Richard Lopez of the Sheriff’s Homicide Bureau said after meeting with coroner’s medical examiners, investigators are convinced that Kelly died as the result of suffocation. He declined to give further details.

DNA linked Munnecke to the killing, leading to his arrest, Lopez said.

As part of the ongoing investigation, detectives obtained a court order to collect a sample of DNA from Munnecke in August of 2010, Lopez said.

While Munnecke had not previously been named as a suspect in Kelly’s killing, “We knew of his connection to the victim,” the detective said.

When results from the DNA analysis came back in September of last year, “it narrowed the investigation,” Lopez said.

Authorities allege the killing took place while Munnecke, who is married, was having an affair with Kelly. Munnecke has denied an affair took place.

Munnecke’s arrest shocked many who knew him as a friendly and active community member.

According to county booking records, he was being held in lieu of $1 million bail pending arraignment Friday in Alhambra Superior Court.