The twins were found dead in a crib in their second-floor apartment at 313 S. Raleigh St. on March 6. When rescue officials arrived, the babies' mother, Jewell Johnson, was attempting to perform cardiopulmonary resuscitation on her children, officials had said.
Johnson could not be reached for comment Tuesday.
At the time, officials said there did not appear to be any signs of foul play.
Martinsburg Police Detective Kevin Miller said he did not want to comment on the case until he receives a written copy of Sabet's report.
Sabet said the cause of death of the infants was not known sooner because of the large number of laboratory tests required.
Toxicology and microscopic tests were conducted on the twins to help determine their cause of death, Sabet said. Microscopic testing involves analysis of skin samples, Sabet said.
There was no sign of injuries on the twins' bodies nor any signs of toxic drugs in their bodies, Sabet said. There also were no signs of carbon monoxide poisoning or hypothermia, he said.
Although the cause of sudden infant death syndrome is a mystery, medical experts have identified some risk factors associated with the complication, said Edward Arnett, a pediatrician in Martinsburg.
For example, babies who sleep on their stomachs rather than their backs have been found to have twice the chance of succumbing to crib death, said Arnett.
Babies who have had prior illnesses or whose mothers smoke also have shown a greater chance of suffering from the complication, Arnett said.
"Unfortunately, there's not a lot that can be done to prevent it," said Arnett.