Authorities are investigating graffiti that included what appeared to be a bomb threat at West Forsyth High, an incident that prompted more than half the students to leave school early Friday.

In a letter sent home to parents and posted on the school’s Web site, West Principal Richard Gill commended students, staff and parents for their patience and understanding throughout the day.

“Through the coordinated efforts of law enforcement, school administration and student information we are confident that our investigation has netted those responsible for this crime,” Gill wrote. “I am proud to preside over a student body that has so much pride in their school.”

Authorities would not confirm Friday whether they had made any arrests in the incident at the campus on Drew Road.

Forsyth County Sheriff’s Lt. Col. Gene Moss said authorities have determined from the school’s video surveillance tapes that at least two suspects were involved.

He declined to release further information about the investigation, other than to say the agency is working closely with school officials and investigators are following leads.

“We got an indirect threat that something was going to happen at 10:45 a.m.,” Moss said.

The indirect threat apparently included the word “bomb” spray-painted on a wall with 10:45 written underneath.

Jennifer Caracciolo, district spokeswoman, said authorities searched the campus for a bomb, but did not find one.

“We were able to pull the video and search before anyone got here, including staff,” Caracciolo said.

The incident was the second involving graffiti at the school this week.

She said school officials discovered Tuesday that someone had spray-painted the school sign and the bus drop-off area, though the messages were not as severe as those found Friday.

Briana Richel, a junior, said she saw the writing on her way into school Friday morning.

“It was just appalling,” she said. “I can’t believe that somebody would be immature enough to go to such levels. The threats were unnecessary.

The whole thing was unnecessary.”

Richel said she stayed at school Friday because she had a test, which was later cancelled because of the lack of students.

When he first saw the graffiti, West sophomore Morgan Gunter said he thought it was a joke.

“A friend of mine was really freaked out,” he said.

Gunter said students are not allowed to use their cell phones in class, but several teachers permitted them to alert their parents of the situation.

“I texted my parents and they were scared for me,” he said. “I knew nothing was going to happen. Some kids thought it was funny. It’s not funny.”

Custodians and bus drivers discovered the writing, which was on every side of the school building, about 6 a.m. Friday.

The school’s American flag was also spray-painted, as was the press box at the stadium and a vehicle in the parking lot.

Although the campus was determined to be safe, many parents removed their children early from school.

Caracciolo said about 800 of the school's 2,000 students checked out through the school office, while as many as 300 more did not leave through the proper channels.

“The problem is that countless students just left or their parents walked in and said that the line is too long and they just took their student,” she said.

While some parents later called or sent e-mails saying they had picked up their children, Caracciolo said the situation could've created a problem.

“If something did happen on campus, we couldn’t account for those students,” she said.

Caracciolo said some parents later brought their children back to school. The campus was calm at its regular afternoon dismissal time.

West senior James Doyle said the graffiti disrupted classes.

“If this is someone’s idea of a senior prank, as a senior I’m offended,” Doyle said. “It’s one thing to take a shot at a school, but when you’re taking a shot at your nation’s flag ... we all live here.

"It’s a symbol of our country and what we stand for and (the graffiti is) giving us a bad name.”

Doyle said he thinks whoever defaced the school deserves to go to jail.

The graffiti named Gill, assistant principal Tom Fowler and school resource officer Alan Seabolt.