NASHUA, N.H. (CBS) —  All public schools in Nashua, NH, will be closed Monday after school officials received a detailed threat of violence involving the city’s two high schools.

State and federal officials are investigating the credibility of the threat.

Superintendent Mark Conrad announced the closures out of an abundance of caution, “because the threat is specific and extends to several schools.”

Seventeen public schools are included in the district with more than 11,000 students. Parents were alerted to the closure through the district’s phone alert system.

Two mothers headed to the Nashua police station when they received the alert.

“I need answers and I am scared,” one mother told WBZ-TV.

Officials would not clarify the nature of the threat, but said a school administrator received the threat through email.

“We’re going to do anything we need to do to assure parents, staff and students that they will be safe in our schools,” Nashua Police Lieutenant Kerry Baxter said.

Administrators said it’s a tough decision to shut down schools for the day.

“For every parent who might say ‘why did you close,’ there will be other parents who say ‘you should have closed if there was a threat,'” Conrad said.

Conrad said the schools are likely to reopen on Tuesday.