(CNN) -- A developmentally delayed teen girl was found Thursday with a person of interest in Rhode Island, three days after she disappeared from a public library in Massachusetts, police said.
"I want to emphasize the fact that she is safe, she is unharmed, she is OK," Medfield Police Chief Robert Meaney said Thursday morning.
Police say Brittany Thompson, 17, of Medfield was last seen Monday leaving the Medfield Public Library with a man.
"Medfield Police Department received a call at approximately 7:30 this morning from the Coventry, Rhode Island, Police Department that Brittany and a male person of interest, that we were starting to look at as part of our conversation, had been located walking down a road in Coventry, Rhode Island," Meaney said Thursday morning.
The man with her was as an adult, older than Thompson, with an address in Missouri, Meaney said. "I don't believe the parents know who this individual was," he added.
The person she was seen leaving with Monday was a heavyset man, wearing a "Sons of Anarchy" T-shirt and slicked-back hair, according to a Massachusetts State Police statement released this week.
"I do not know if the person she was found with was the person on the surveillance video ... that's one of the things we are trying to make sure of," Meaney said.
"In the videotape, she looks like she walks out of the library voluntarily," he told CNN on Wednesday.
Meaney said Thompson's family headed to Coventry and were probably reunited with Thompson early Thursday.
No charges have been filed, but an investigation is ongoing. Police are not releasing the name of the man considered a person of interest.
"There's a lot of pieces to the puzzle that we have not yet put together," Meaney said.
Thompson was not taken to a hospital when she was found and did not appear to have any injuries, he said.