Authorities have a woman in custody who is considered a person of interest in the case of a young boy found dead on the side of a back road near the Maine-New Hampshire border, authorities said.

The woman agreed to be interviewed by authorities at the Concord Barracks, and late Wednesday afternoon, the woman was transported to a nearby hospital for medical evaluations, David Procopio, a spokesman from the Massachusetts' State Police, said. The woman is in custody but she has not been charged.

Procopio would not go into specific details about the investigation and referred reporters to the New Hampshire Attorney General’s Office. However, he said that new information on Wednesday is unlikely.

At 10:12 a.m., state police received a tip about a navy blue Toyota Tacoma pickup truck, which led them to the woman. The public was aware that a similar truck was seen in the area the boy was found.

Meanwhile, investigators are working to identify the boy, believed to be between between 4 and 6 years old.   

The U.S. Navy's elite police unit joined the investigation after a witness reported seeing a Navy emblem on the license plate of a pickup truck that was spotted in the area.

Investigators from the Naval Criminal Investigative Service are going to military installations in the Northeast in hopes of being able to identify the boy, his body discovered Saturday beside a back road in South Berwick.

Investigators say the boy may have been placed on Dennett Road -- just off Route 4 -- at around 7:30 a.m. Saturday. The child, described as 3 feet 8 inches tall and weighing 45 pounds, likely died about two hours earlier, police said. Authorities have not yet released how the boy died. 

There is no missing person's report that matches the description of the child, authorities say, and a computer-generated photo of the boy has been released in hopes it will garner leads.

Lt. Brian McDonough with the Maine State Police has pleaded with the public for help in identifying the child. 

"Somebody has got to miss this child, (whether) it's the nephew of somebody or the grandson of somebody, to that end, it's been very, very frustrating that we haven't gotten any leads, significant leads, on identifying this child," McDonough said Monday.   

Meanwhile, about 400 people attended a candlelight vigil for the boy outside the South Berwick Town Hall Tuesday evening.

Vigil organizer Amy Aiguier says no human being should be unidentified.

"I'm just sad no one's claimed him," Heidi Hilton of Somersworth, N,H., told "A million people are here today to claim him, but his family hasn't claimed him."

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The Associated Press contributed to this report