The newspaper quoted the state's public health officials as saying that the deaths, which were reported in the past nine days in the county, added to 141 other fatal incidents linked to opioid fentanyl consumption since June.
Seattle Public Schools have distributed warnings to students and families about the risks of buying drug pills at online shops.
"Pills purchased online are not safe," said the warnings issued by public health authorities in Seattle and King County.
A 17-year-old student died of fentanyl intoxication on Sept. 29, followed by the killing of a 16-year-old from Skyline High School on Sept. 30, when the school witnessed the second similar death in seven weeks, said the newspaper.
A total of seven teenagers have been killed by fentanyl overdoses in King County this year, according to the daily.