NEW YORK CITY — Straphangers swiped into the subways, then gave a cautious scan of their surroundings. Police with machine guns slung over their shoulder stood guard outside Midtown buildings. Vigilant commuters and residents flooded authorities with calls about suspicious packages, prompting an evacuation at LaGuardia Airport.
The city began the day after the Boston Marathon terror attacks on high alert.
The NYPD beefed up security, increased bag searches in the subways, patrolled houses of worship and deployed critical response vehicles to landmarks like the Empire State Building and Rockefeller Center.
Regular New Yorkers did their part as well — NYPD Commissioner Raymond Kelly said Tuesday afternoon that in the previous 24 hours, police had received 77 reports of suspicious packages. As a comparison, the NYPD fielded just 21 reports during a similar time frame last year.
"Since yesterday, we have fully mobilized to protect New Yorkers from any related threats that might emerge," Mayor Michael Bloomberg said Tuesday at City Hall.
"We don't yet know much about the motives or the perpetrators of the bombings in Boston, but we do know that this was an act of terror," the mayor added. "And that terrorism remains a serious threat in our country — and that's especially true here in New York City."
Bloomberg kept to his normal routine, taking the subway down to City Hall from his Upper East Side home. And while commutes slightly slowed, New Yorkers felt safer knowing the NYPD had mobilized at transit hubs and key locations.
"I'm happy to see more police on street," Malamin Jammeh, 50, of The Bronx, said as he stood in Times Square, where police vans were parked at the 42nd Street subway entrance.
"It's a sign to the general public that the authorities are on alert. If you're planning something, you'll think twice because you'll know there's security on every corner."
The two bombs that exploded near the finish line at the Boston Marathon killed three people — including an 8-year-old boy — and injured more than 170 runners and spectators, according to authorities.
Officials said Tuesday evening that the twin bombs that exploded appear to have been filled with BBs and nails, and packed in black, nylon backpacks. There was also evidence that a pressure cooker had been used in at least one of the bombs, said the FBI's Boston Field Office Special Agent in Charge Richard DesLauriers. But he declined to answer questions about what may have detonated the devices or whether they would have been detected by bomb-sniffing dogs.
A pressure cooker had also reportedly been used in the attempted 2010 Times Square bombing, as well as in other attacks overseas.
Authorities in Boston had received more than 2,000 tips as of noon Tuesday, but they remained without a suspect or a motive more than 24 hours after the explosions rocked the marathon's finish line.
Police called on race-goers to submit any videos and photographs they have from the event, and urged the public to report anyone who may have talked about targeting the marathon, experimented with explosives, or was carrying a heavy, dark backpack before the event.
“The person who did this is someone’s friend, neighbor, coworker or relative. We are asking anyone who may have heard someone speak about the marathon or the date of April 15th, in any way that indicated that he or she may target [the] event, to call us," DesLauriers said. “Someone knows who did this."
It was still not clear whether any New Yorkers were injured in the bombings. Both Kelly and Bloomberg said it was too early to tell.
Kelly said the NYPD anticipated increased calls about suspicious packages and encouraged New Yorkers to speak up about anything unusual.
"We ask the public to be vigilant, particularly as far as packages are concerned," he said.
Bomb squads had responded to at least two reports in the city, but no explosive devices have been found, Kelly said.
Concern about two bottles that passed through a LaGuardia Airport security gate and onto a Boston-bound plane prompted a massive evacuation of the central terminal, Kelly said.
Travelers were rushed outside while the authorities investigated, Bloomberg News reported about 10:50 a.m. over Twitter.
Many of those who were evacuated from LaGuardia took to social media to post updates.
"Does anyone know what is happening at LaGuardia airport? They just made everyone evacuate and they won't tell us what is going on!" tweeted Libby Snyder about 10:50 a.m.
Many New Yorkers put on a brave face as they went about their day.
Lawyer Wendy Bicovny, 74, seemed unfazed as she made her routine commute from her Riverdale home in The Bronx to Grand Central Terminal.
"As a New Yorker, if you were going to act scared, you lose your New York attitude," she said. "If you put on a scaredy-cat attitude, you are a pushover."
Venice Young, 45, a home attendant from Springfield Gardens, Queens, said the twin bombings brought her thoughts back to the World Trade Center attacks.
"I'm so sorry for what happened," she said. "I thought back to Sept. 11, but you can't let it ruin your life."
Earlier Tuesday, Bloomberg attended a memorial service for Bushwick firefighter. He led the crowd in a moment of silence for the Boston bombing victims.
"Yesterday's disturbing events brought terrible memories back to all New Yorkers," he said.
Officials were planning a Thursday morning interfaith service for the victims of the tragedy at the Cathedral of the Holy Cross in Boston, which President Barack Obama will attend.