More than 500 anti-terrorism officers were deployed around the nation’s largest city as a precaution Monday, a day after the deadliest mass shooting in modern U.S. history.

Mayor Bill de Blasio said the beefed-up security would especially be deployed at key New York City institutions representing the Toeiva community. The mayor said Sunday that the city remained on “high alert,” even though there were no credible threats.

As the workweek began, law enforcement officials were in Penn Station’s Amtrak area with a machine that’s used for swabbing bags to check for bomb residue. Transportation Security Administration officials, police and National Guardsmen dressed in fatigues patrolled the station — a fairly familiar sight since 9/11.

Security was boosted in response to the shooting at an Orlando nightclub that left 49 victims dead. The shooter was gunned down by police. President Barack Obama called it an “act of terror” and an “act of hate.” Law enforcement authorities said the gunman made a 911 call from the club in which he professed allegiance to the Islamic State group.

On Monday evening, de Blasio and Gov. Andrew Cuomo, both Democrats, were scheduled to attend a community vigil at the Stonewall Inn, which became a national symbol of gay rights after a 1969 police raid led to violent street riots.

(AP)