PEPPER PIKE -- Many students stayed home Thursday as a high school closed for three days by bomb threats re-opened. Attendance at Orange High School was only 60 percent, according to district spokeswoman Stacy Vincent.

She described the mood at the school as "good, and cautiously optimistic." School district officialsheld a newsbriefing Thursday afternoon to address both the continuing bomb threats and the successful restart of classes.

"In this difficult time, the presence of the students and the staff is our best defense against this intimidating fear," Principal Dr. Paul Lucas said after classes were dismissed Thursday.

The school reopened under tight security as police and FBI agents tried to identify the source of emails that threatened blacks and Jews, issued bomb threats, and forced the cancellation of classes for three days.

No bomb was found and Orange High School classes resumed without incident, district spokesman Lou DeVincentis said. Of the 750 students enrolled, only about 450 actually came to school on Thursday. Approximately 300 stayed home.

"I feel confident. I feel safe," principal Lucas told WKYC Thursday morning. "I wouldn't be here if I didn't feel the school was safe. We definitely have it secured and we have the school building safe and cleared."

As the building opened for the first time this week, book bags and backpacks were banned as a security measure, and students weren't allowed to go to their cars during the day. Extra police were assigned to patrol the grounds.

"Though attendance was down today, those students who attended helped to diffuse the fear that was caused by this threat," said District Superintendent Dr. Nancy Wingenbach during an afternoon news briefing.

The threateningemails referred to the Ku Klux Klan and made threats against blacks and Jews, two big segments of the enrollment. The latest email threat, which was copied to WKYC-TV, was received at about 1 a.m. Thursday.

The school closed Monday through Wednesday while searches were conducted with bomb-sniffing dogs.

The FBIand Pepper Pike police wereworking to identify the sender, who took measures to avoid being traced.

Superintendent Wingenbachemphasized in a message posted on the district's website that appropriate and necessary procedures were followed to ensure the high school and other campus facilities were safe.

"Many of the rumors circulating are not substantiated and should not be treated as factual," she stated Thursday afternoon. "We will continue to have increased police presence on campus and tighter access to each building, beyond our usual safety measures."

The district covers some of Cleveland's wealthiest suburbs including Pepper Pike, Orange, Hunting Valley, Woodmere and Moreland Hills.