Boston Baby Doe’s mother, Rachelle Bond, has been arrested over the girl’s death, police in Massachusetts say.

Three-year-old Bella Bond was found dead months ago in a plastic bag on the shore of Deer Island in Boston

Rachelle Bond’s boyfriend, Michael McCarthy, who is not Bella’s biological father, is to be charged with the girl’s murder.

Called “Baby Doe” by Boston police, the girl’s body was found by a woman walking her dog on June 25. The girl was finally named on September 18 as Bella Bond.

Police commissioned a computer-generated image to help identify Baby Doe which was shared millions of times.

At a news conference on September 18, Suffolk County District Attorney Daniel Conley said police had received a tip-off which had allowed them to solve the mystery.

He said he had authorized the arrest of Rachelle Bond, 40, as an accessory to murder, and her partner, Michael McCarthy, 35, for murder.

Rachelle Bond is in custody, while Michael McCarthy is in hospital being treated for an unrelated medical condition, Dan Conley added.

“At just shy of three years old, Bella Bond was a true innocent,” he said.

“This child, whose very name means beauty, was murdered.”

Daniel Conley did not comment on how Baby Doe died or on any possible motive. No signs of trauma have been found on her body.

The case received a massive response on social media and drew thousands of new visitors to government websites.

Police received hundreds of tips from the public, but they were unable to find anyone who knew the girl until now.