US authorities investigating whether an American teenager was a child who famously disappeared in 2011 have found he is not the missing boy.

The Federal Bureau of Investigation in Louisville said on Friday (AEDT) that DNA tests on the teenager found covered in bruises and wandering the streets earlier in the week was not missing boy Timmothy Pitzen.

“DNA results have been returned indicating the person in question is not Timmothy Pitzen,” the FBI’s Louisville branch posted on Twitter.

The 14-year-old phoned police on Thursday (AEDT) and said he’d just escaped from two kidnappers after more than seven years of captivity.

He identified himself as Timmothy Pitzen, an Illinois boy who vanished in May 2011 aged six during a road trip with his mother Amy Fry-Pitzen, who took her own life in a local motel soon after. 

Ms Fry-Pitzen left a note at the time of her death said: “Tim is somewhere safe with people who love him and will care for him,” ABC7 Chicago reported Wednesday.

“You will never find him.”

FBILouisville, @FBICincinnati, @AuroraPoliceIL, Newport PD, @CincyPD, and HCSO have been conducting a missing person investigation. DNA results have been returned indicating the person in question is not Timmothy Pitzen.

— FBI Louisville (@FBILouisville) April 4, 2019

The case drew widespread attention, and a search spread across Illinois, Wisconsin and Iowa was unable to locate the missing child at the time.

Timmothy’s family has heard of multiple false sightings of the missing boy over the years, but his aunt, Kara Jacobs, said this had been the most promising development.

“We always felt very strongly that Tim was alive,” Ms Jacobs said.

“What I’ve prayed about since he’s been gone is that God will keep him close and take care of him. And that maybe, by some stroke of luck, he was with people who would love him.”

She said Timmothy’s father was “trying very hard to hold it together” as he awaited confirmation of the teenager’s identity.

The police department in Sharonville, Ohio, was one of numerous agencies asked by Kentucky authorities to help search local motels for the men who the teen said had been holding him, Sharonville police chief Steve Vanover told Reuters.

However, details of the case remained murky.

“We still have no confirmation of the identity of the person located, but hope to have something later this afternoon or early this evening,” Aurora police tweeted Thursday night.

A police report filed by a Sharonville detective summarised a dramatic story of escape from kidnappers, which Mr Vanover said was told to Sharonville police by officials in Campbell County, Kentucky.

Mr Vanover said he could not confirm whether the account was true.

The teen said he had been held by two white men for seven years and had escaped from them and run across a bridge from Ohio into Kentucky.

He described the men as “body-builder types” and said they were driving a Ford SUV and staying at a Red Roof Inn, a summary of the Campbell County request said.

The teen was taken to hospital but no information has been released on his condition.

The FBI said it was working with police and other agencies on a missing child investigation, but offered no further information and did not identify a child.

-with AAP