But hours later the case took yet another turn: Sanchez had apparently faked the whole thing, according to local media.
Citing police officials, The New York Times and CBS News New York reported Tuesday evening that Sanchez orchestrated the kidnapping because she was upset with her mother.
A New York Police Department spokeswoman declined to comment on the reports Tuesday evening. It was not immediately clear whether Sanchez or the men who pulled her off the street will face charges.
The chain of events was met with a mix of relief and frustration as shock over her disappearance gave way to questions about whether the alleged hoax would undermine other missing-children investigations.
Karol Sanchez disappeared about 11:20 p.m. Monday as the mother and daughter were walking in the Bronx's Melrose neighborhood.
As of Tuesday night, police had not disclosed how they located her or said whether they had identified any suspects.
New York Police Department Deputy Inspector Robert Gallitelli said in a tweet that police were grateful "to all who have worked very hard to track down the people involved in this case."
"WE HAVE A VICTORY TODAY," Gallitelli wrote. "Karol Sanchez has been located in the Bronx, she is safe and unharmed."
"Thank you to the men and women of the NYPD for their quick work - and to every single New Yorker who came forward with information," New York Mayor Bill de Blasio, a Democrat, tweeted Tuesday.
Video posted Tuesday afternoon showed police reuniting a tearful Sanchez with her family, with news cameras hovering nearby. She and her relatives didn't comment as officers escorted them away.
Carmen Sanchez, 36, refused medical treatment after she was pushed to the ground, a spokesman for the New York Police Department told The Washington Post. She described the vehicle to police as a beige four-door sedan that stopped before fleeing eastbound after the incident. In addition to the two men who snatched Karol Sanchez, two other men were in the car and were described as young-looking, possibly in their mid-20s, and wearing dark-colored clothing.
The mother and daughter are from Poughquag, New York, roughly 60 miles north of the Bronx, and were in the city for a doctor's appointment earlier Monday, NBC News New York reported.
City officials tweeted out the alerts Tuesday morning, calling for help to bring Sanchez home.
"To Karol Sanchez's family and loved ones, know that the NYPD will not rest until she's found - and her kidnappers are brought to justice," de Blasio wrote.
New York State Police activated an Amber Alert for the teen's kidnapping at 10 a.m. Tuesday. State police were not part of the ongoing investigation, but the agency is responsible for issuing the alerts, state police spokeswoman Kristin Lowman told The Post.
"Our special victims unit evaluates [an agency's call] to decide if they should activate an alert," Lowman said. Amber alerts are activated in New York only in cases where a minor is abducted and "believed to be in danger of serious bodily harm or death," according to the the state police's Amber Alert criteria.
