A man who helped rescue an abducted 15-year-old girl has gifted his reward money of around $9,000 to the teenager and her family, saying they need it more than him.

Jasmine Block disappeared from her home in Alexandria, Minneapolis on August 8 after she was approached by 35-year-old Thomas Barker, a family acquaintance, who said he needed help with a "family situation".

Police say the teen went with Barker in his car and when they arrived at his home, he tied her up with zip ties.

She escaped 29 days later, and was spotted by local man Earl Melchert in a field on his property. He immediately alerted police.

"I thought at first it was a deer," Mr Melchert said.

"I could make out her face, and I went, 'Oh my gosh, this is the girl from Alexandria that's been gone for 29 days'."

On Friday (local time) the Alexandria Police Department presented Mr Melchert with $US7,000 in reward money, but he did not accept.

"He believes that young lady that came running towards him that September day is the real hero and without hesitation, Earl handed the reward over to her, followed by a big hug," the Alexandria Police Department said on Facebook.

"Thank you Earl, it is people like you that make this world a better place."

Mr Melchert said it was "the best thing I've ever done".

"The family needs the money," he said.

"To me, yeah, that's a lot of money, but they need it way worse than I do."

Mr Melchert was presented with the reward money but he did not accept. ( Facebook: Alexandra Police Department )

An 'unbelievable young woman'

During the time Ms Block was held, she was physically and sexually assaulted and threatened with weapons by Barker and two other men, police said.

The men then took Ms Block to several locations, including a corn field.

Alexandria Police chief Richard Wyffels said Ms Block escaped from a nearby abandoned house when her captors left her to buy food.

"This was the first time she'd been left alone in 29 days," Mr Wyffels said.

When Ms Block escaped she ran to several properties to find help, before eventually swimming across part of Thompson Lake, Grant County.

Soon after she found Mr Melchert.

Three men — Barker, Joshua Holby, 31, and Steven Powers, 20 — have been arrested and are being held in the Douglas County jail.

Mr Wyffels said Ms Block was an "unbelievable young woman".

"We are all proud of her," he said.