Charlotte Sena was last seen at around 6.15pm on Saturday at Moreau Lake State Park in Saratoga County, which is 50 miles north of Albany, the capital of New York State.

Police believe Charlotte was taken under circumstances that mean that she is in "imminent danger of serious harm and/or death". An amber alert for a "child abduction" was activated by police on Sunday morning.

It is believed she was wearing an orange tie-dye Pokemon T-shirt, dark blue trousers, black Crocs and a grey bike helmet when she disappeared.

More than 100 personnel and 75 law enforcement officials have since been deployed in the search, which also includes dogs, two drones, boats and six underwater rescue teams, according to Ms Hochul.

"We just want her returned safely like any parent would. No tip is too small, please call if you know anything at all," her family said in a statement to Sky News' US partner network NBC News.

New York Governor Kathy Hochul told reporters that Charlotte and her family were camping only 15 minutes from where the girl and her sisters were raised.

Ms Hochul said the nine-year-old had been riding Loop A of the park with family friends when she said she wanted to do one more lap by herself.

When she didn't return 15 minutes later, her parents and nearby campers began to search the area.

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At 6.45pm local time, the bike Charlotte was riding was found.

Having met with Charlotte's family, Ms Hochul said: "As a mother and as a grandmother, I cannot imagine the pain they're going through.

"Hopefully there will be a reunion, hopefully, there will be a family that has been traumatised but reunited."