A 9-year-old US girl who vanished during a family camping trip in upstate New York was found safe on Monday following a two-day search, authorities said.

Charlotte Sena was located “in good health” and “a suspect is in custody” in connection with her disappearance on Saturday evening, New York State Police said in a statement.

Authorities didn’t immediately release further details.

Hundreds of law enforcement officers, forest rangers and others searched a swath of upstate New York after the girl disappeared while riding her bicycle in Moreau Lake State Park, about 60km north of Albany, according to state police.

Police had said they were worried she was abducted.

The girl’s family pleaded with the public for help in finding Charlotte, including providing any tips to the state police.

“We just want her returned safely like any parent would,” the family said in a statement. “No tip is too small, please call if you know anything at all.”

About 400 people took part in the search Monday, up from more than 100 the day before, state police said. The searchers included state and local police, forest rangers, local volunteer firefighters, and some private search and rescue groups, officials said. Authorities also requested help from the FBI.

Gov. Kathy Hochul said on X, formerly known as Twitter, that she was “Extremely grateful to @nyspolice, @NYStateParks police, and all of our partners who worked tirelessly to locate Charlotte and ensure she could return home safely to her family.”

The search expanded over 74 linear kilometres by Monday, with much of the area heavily wooded.

Bloodhounds were used in the search for a missing 9-year-old girl. Photo / AP

Troopers set up several checkpoints on the winding, rural roads around the park. They stopped drivers and asked if they knew the family, had seen the girl’s photo or had any other information that could help the search. They also had some drivers open their trunks.

The park remained closed because of the search, and officials asked members of the public who showed up hoping to help to stay away and leave the search to professionals. Federal authorities also issued a temporary flight restriction over the park for the safety of law enforcement air operations.

“Charlotte is a bright and adventurous girl who loves to be outside,” state police said in a statement. “Charlotte has a huge heart and wants to create a club at her school for kids who don’t have friends. She always put others first. Please know that we continue to work around the clock to bring Charlotte home.”

Charlotte Sena, 9, who vanished during a camping trip in upstate New York. Photo / AP

Charlotte, a fourth grader from nearby Greenfield, had been riding her bike around a campsite loop in the bucolic park with other children when she decided to ride around one more time by herself. Her parents became alarmed when she failed to return after 15 minutes, Gov. Kathy Hochul said at a briefing Sunday.

The girl’s mother called 911 after her bicycle was found around 6.45pm on Saturday.

Officials issued an Amber Alert on Sunday morning after an exhaustive search because “it was quite possible that an abduction had taken place,” state police Lt. Colonel Richard Mazzone said. The alert described her as a white girl with blonde hair and green eyes who is about 1.37 metres tall.

She was last seen wearing an orange tie-dye Pokemon shirt, dark blue pants, black Crocs and a grey bike helmet.

The Corinth Central School District said it had extra counsellors at Charlotte’s elementary school for any students or staff who need support.

“Our hearts go out to the Sena family,” the district said in a statement.