LOS ANGELES, United States (AFP) – Los Angeles city officials defended their decision to shut down all public schools on Tuesday in response to an email threat that appears to have been a hoax.

The drastic measure was ordered as a precaution, triggered in part by the December 2 attacks in nearby San Bernardino that left 14 people dead, said Ramon Cortines, the superintendent of Los Angeles schools — the second-largest school district in the US with 640,000 students.

A similar threat was also made against New York City schools, but officials there said they deemed it not credible from the onset and accused Los Angeles school officials of badly overreacting.

Later in the day, California Congressman Adam Schiff said the email, which was sent late on Monday from an IP address in Frankfurt, Germany, was likely a prank.

“Preliminary assessment is it was a hoax to disrupt school districts in large cities,” Schiff said in a Tweet.

Cortines told a news conference that the alarm was raised after several members of the school board reported receiving an email threatening violence involving backpacks and packages left at some of the district’s 900 schools.

“In an abundance of caution, we have chosen to close our schools today until we can be absolutely sure that our campuses are safe,” said the school district’s police chief, Steven Zipperman.

California Congressman Brad Sherman told CNN that the email had come from a person claiming to be a “extremist Muslim” who said attacks would take place on Tuesday and would involve nerve gas.

The message also said the person boasted of having “32 accomplices… all ready to take action today,” Sherman said.

But in biting criticism, New York Police Commissioner Bill Bratton said Los Angeles school officials’ action was “totally, totally uncalled for.”

“It’s what they want, whether it’s a prankster or a terrorist, they want to instill fear,” Bratton told reporters.

Bratton, who previously served as Los Angeles police chief from 2002 to 2009, said the person behind the threat may have been inspired by the hit television series “Homeland.”

New York Mayor Bill de Blasio told a press conference that the threat was “so generic and outlandish” that it could not be taken seriously.

Bratton’s comments prompted a rebuke by the Los Angeles police chief Charlie Beck, who insisted the school shutdown was justified with the children’s safety paramount.

Authorities ordered all public transport in Los Angeles to be free of charge for students to enable them to get home or move about the sprawling West Coast city.

Private schools in the district remained open since the threat was only directed at public schools.

The Los Angeles Unified School District comprises more than 21,000 buildings spread over 720 square miles (1,865 square kilometers) within Los Angeles and nearby communities.

California has been stunned by the massacre in San Bernardino, about an hour east of Los Angeles, carried out by US-born Syed Farook and his Pakistani wife Tashfeen Malik.

The Muslim couple were killed in a shootout with police following the attack, which the Federal Bureau of Investigation is treating as an act of terrorism.

According to a new Wall Street Journal/NBC News poll released on Monday, national security has become the top issue of concern for Americans in the wake of the San Bernardino assault and the recent deadly attacks in Paris.