WASHINGTON (AFP) - Authorities in the northeastern US city of Nashua said they ordered schools closed on Monday (Dec 21) following a threat, less than a week after Los Angeles city officials took a similar decision.

"We have received a detailed threat of violence to harm students and staff at both high schools," Mark Conrad, superintendent of the Nashua School District, said in a statement Sunday.

"Because the threat is specific and extends to several schools we will be cautious and close all of our public schools in Nashua," a city of around 87,000 people in the state of New Hampshire.

The decision to keep students at home comes less than a week after authorities in Los Angeles took the drastic step of closing more than 900 schools after receiving an emailed threat.

In the end, the threat was not deemed credible.

Conrad said that the district was working closely with police to determine whether the threat was credible and said he expected classes to resume on Tuesday.

New Hampshire Governor Maggie Hassan said the state police and emergency management officials were working closely with the Nashua Police Department, local public safety officials and the FBI on the matter.

"Public safety is any government's most important responsibility - especially at our schools - and we are closely monitoring the situation in Nashua," she said in a statement.