A King’s Fork Middle School student has been charged with writing a bomb threat on a stall in a girls’ restroom at the school, according to a letter sent home to parents Tuesday.

The latest in a string of similar messages in a handful of Suffolk’s public schools was found by a student Monday morning and reported to a teacher, Principal Jennifer K. Presson wrote in the letter.

“We were certain that these messages were written that day as the stalls were clean that morning at the time of the morning inspection,” Presson wrote. “As the message was not considered credible, we proceeded with the investigation without an evacuation or lockdown.”

The student has been suspended for 10 days pending an expulsion hearing, and criminal charges have been filed.

On Tuesday, a message was found in one of the boys’ restrooms, Presson added. Steps put in place to monitor restrooms and common areas after the threats began have “helped narrow the field of suspects through the use of video surveillance,” Presson wrote in the letter.

Suffolk Public Schools spokeswoman Bethanne Bradshaw said the videocameras are set up in hallways, not in the bathrooms.

Another bathroom wall message was found at King’s Fork High School Tuesday afternoon. An automated call informed parents that the message, written on a boys’ bathroom wall, indicated someone was going to blow up the school Wednesday. Police and fire investigators are conducting an investigation, which may have revealed a possible suspect, according to the message.

The threats follow another three similar threats at King’s Fork Middle School, as well as one other at King’s Fork High School and two at Lakeland High School.