Detectives say their technology is so advanced that they can trace most phone calls, but there are still some bomb threats that are outstanding.
Wood County Prosecuting Attorney Ginny Conley says only one of the bomb threats made to Parkersburg High School last fall has been solved.
She says a juvenile responsible for the crime has already been put through the justice system.
She also says the two at Parkersburg South were linked to one person.
That juvenile has also been brought to justice.
Conley says she has chosen not to release 911 tapes for fear of jeopardizing the investigation.
"The 911 tapes in any criminal investigation, the rules of ethics prevent us from taking this information and disseminating it to the public. There are certain rules of ethics that, as a prosecutor, I am responsible for and my office is responsible for," said Conley.
The bomb threat during the PHS prom is also outstanding.