MANCHESTER - Threats of violence today at the city's high schools, amid predictions of the end of the world and in light of the tragic killings in Newtown, Conn., are unsubstantiated rumors, according to the school superintendent.

Police are working closely with school district officials in the investigation of the rumors 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, Conn., and the predictions 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."

Other schools also reported receiving threats included Derry and Windham.