The NYPD and Mayor de Blasio said New York City school officials received the same anonymous threat that prompted Los Angeles to shut down its public schools Tuesday, but authorities said they determined the email to be "not credible" and were investigating it as a hoax.

De Blasio and Police Commissioner Bill Bratton said several other districts nationwide also received a generic email threat Tuesday, but investigators determined that students weren't in any real danger.

New York City schools will remain open Tuesday, de Blasio said.

"Our schools are safe. Kids should be in school today," the mayor said. "We will be vigilant. But we are absolutely convinced our schools are safe."

Bratton said that officials in the Los Angeles Unified School District — which, with more than 640,000 students, is the nation's second-largest school system, second only to New York City — overreacted by canceling classes. He said that's what whoever made the threat wanted.



Both Los Angeles Mayor Eric Garcetti and Police Chief Charlie Beck defended the decision by their city's superintendent to shut down the more than 900 schools, saying it was a tough decision but the safety of students and employees was the main concern.

Police say a man upset with hotel staff slammed his truck into the building’s lobby, narrowly missing front desk workers.

Bratton said that the emailed threat is being investigated as a hoax. He said the person who wrote the note claimed to be a jihadist, but made errors that made it clear the person was a prankster, including spelling the word "Allah'' with a lowercase "a.''

Bratton, who once ran the Los Angeles Police Department, quipped that it looked like the sender watched a lot of the show "Homeland.''

"We cannot allow ourselves to raise levels of fear,'' Bratton said.

Law enforcement sources tell NBC 4 New York that the emails sent to both New York City and Los Angeles officials included very similar wording and mentioned bullying. The email writer said he or she went to Los Angeles schools in the messages sent to that district, while the ones sent to New York mentioned that the writer went to New York City schools.



According to the Associated Press, which obtained a copy of the email, the note warned every school in the city would be attacked by the writer and "138 comrades" armed with pressure cooker bombs, nerve gas agents, machine pistols and machine guns.

New York City's public school system is the largest in the country, with more than 1.1 million students taught in more than 1,800 schools.

In a statement, New York City Schools Chancellor Carmen Farina said the Department of Education is working closely with NYPD and reiterated "there is no reason for alarm."

"As always, the safety of our students and staff both in and around schools is our number one concern and any extra needed security measures will be taken,” Farina said.

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--Jonathan Dienst contributed to this story.