WINDHAM - Windham schools had an additional police presence Friday after a school board member received news of a threat made over the Internet, believed to be against the Windham school district, late Thursday night.

Concerns about violence in local schools also prompted Manchester's superintendent to write a letter to parents about rumors swirling on social media, seeking to ameliorate worries about student safety.

In Windham, Superintendent Henry LaBranche said it's unclear at this point if the threat in town was a credible one, but he was not taking any chances.

"This week we've already been on high alert," he said Friday morning.

School officials learned of the threat around 9:20 p.m. Thursday, when the principal of a parochial school in Willimantic, Conn., contacted a Windham School Board member.

LaBranche said the Connecticut school district, also known as Windham, received threats via Twitter, but school officials there were later told "that the threat was intended for Windham, New Hampshire."

By 10 p.m. Thursday, both the FBI and New Hampshire State Police had been notified, and the incident was being investigated.

"We immediately put our emergency plan into place," said LaBranche. The exact nature of the threat wasn't revealed, LaBranche said. "There are a bunch of 'unknowns.' "But we're being very cautious."

Parents were notified by email Thursday night. Police have already been visible at the district's schools this week in the wake of the deadly shootings at Sandy Hook Elementary School in Newtown, Conn.

Windham police have been making "rolling patrols" at each school since Monday, and school administrators have been taking a closer look at each school's security measures, officials said.

During Monday's school day, Windham High School was briefly placed on lockdown after several school employees reported hearing "a loud bang" inside the school that morning, officials said. Police and fire officials conducted a sweep of the building, although Windham Police Chief Gerald Lewis said "nothing out of the ordinary" was found.

Threats of violence Friday at Manchester's high schools - amid predictions of the end of the world and in light of the killings in Newtown - were unsubstantiated rumors, according to the school superintendent. Police in Bedford likewise dealt with a hoax bomb threat.

In an email to parents, Lurgio Middle School Principal Ed Joyce said a note with a bomb threat was found in a bathroom at Bedford High School Friday morning.

"Although the Police again classified the message as a "low level" threat, we took all appropriate actions to ensure the safety of our students," Joyce wrote. "This time, we moved the students to safe locations in the building: the dining hall and gymnasium. With the students in a secure location we had the building searched by a State Police Canine."

No bomb was found, the campus was reopened and students were allowed to go home, he wrote.

In Manchester, police are working closely with school district officials into the investigation of talk of pending violence and "any other rumor that threatens the safety and welfare of our students and staff," Superintendent Tom Brennan wrote in a letter addressed to the Manchester community.

His letter follows:

"In light of the recent tragic event in Newtown, CT and the predications relative to the end of the world (Mayan calendar), there has been increased chatter on social media regarding acts of violence which has added to the anxiety and fear among parents, students and staff.

"Like many school districts throughout the state, we have become aware of several rumors involving violence directed at our students and staff. We take any threat seriously and with the assistance of the Manchester Police Department, our building level administrators have followed up on these rumors and have determined that these rumors are unfounded.

"The Manchester Police Department continues to work closely with our District in the investigations of these rumors and any other rumor that threatens the safety and welfare of our students and staff. It has provided and continues to provide the appropriate level of resources to maintain the safety and welfare of our students and staff.

"Our building administrators and staff under the direction of the building principals have increased their level of vigilance and continue to be visible throughout the buildings to reduce the levels of fear and/or anxiety among the students.

"The safety and welfare of our students and staff is our number one priority."

aguilmet@newstote.com