FOUNTAIN VALLEY (CNS) - An emailed threat of a bombing and mass shooting  prompted officials to cancel classes at Fountain Valley High School today and  orchestrate a search of the campus for explosives.

A message posted on the school's website said, ``FVHS has been closed by  the FVPD due to a threat overnight. All classes are canceled until further  notice.''

Fountain Valley police said the email, sent from a student's account  about 10 p.m. Tuesday, warned that there would be explosives hidden on campus.

Sgt. Tony Luce said the email also stated that the assailant would go to  the campus after the explosion ``with an assault rifle and kill any surviving  people on campus.''

An Orange County sheriff's bomb squad was sent to search the campus,  according to the Orange County Sheriff's Department. A sweep of the campus,  conducted with the help of bomb-sniffing dogs, did not find any evidence of  explosives.

The campus was cleared by late morning, and school officials posted an  updated notice on its website, saying classes would resume Thursday.

``We will resume afternoon activities as scheduled, such as sports  practices and such,'' according to the notice. ``Staff is welcome to return  today. Classes for the day are canceled and we will resume on a regular bell  schedule tomorrow.'' 

Investigators went to the home of the 17-year-old student who appeared  to have sent the threatening email, but he denied any involvement, Luce said.

``Officers have been to the student's house and contacted the student,''  he said. ``The student indicated that he did not send the email. He's allowed  officers to look at his phone and his computer and they found no evidence that  the email came from him directly.

``When they found no indication that the email came directly from him,  it's quite possible that in some way the student's account was hacked,'' Luce  said.

The student apparently did not have any access to firearms, Luce said,  adding that investigators would conduct a forensic examination of the student's  computer for clues in their search for the culprit.