Update, 5:16 p.m.: Law enforcement officials have identified the child known as "Baby Doe" as Bella Bond, and her mother and her mother's boyfriend have been arrested in connection with her murder.

Suffolk District Attorney Dan Conley said Friday afternoon Bond died in an act of violence in her home in the Boston neighborhood of Dorchester.

“Her name was Bella,” Conley said.

Her mother's boyfriend, Michael McCarthy — who is in Beth Israel Hospital with an unrelated illness — has been arrested for murder. Her mother, Rachelle Bond, is under arrest for accessory to murder. The state took Bond’s two older children away several years ago. They were adopted by Bond’s mother.

"We allege that McCarthy caused Bella's death," Conley said. "That he did so intentionally. That he and Bond took specific steps to keep Bella's death a secret, and to avoid prosecution."

At nearly 3 years old, Bella Bond had been under state supervision for neglect twice — but those cases had been closed.

The child was found in June by a woman walking her dog. She was in a black trash bag that had been placed, or had washed up, on an island that’s home to Boston’s wastewater treatment plant.

"For nearly three months, we have endeavored to speak for a true innocent who could not speak for herself," said State Police Colonel Richard McKeon.

McCarthy and Bond are set to be arraigned Monday.

— Rupa Shenoy

Update, 2:49 p.m.: Unconfirmed reports continue to swirl about the identity of the child found dead in June on the banks of Deer Island.

At a press conference, Gov. Charlie Baker said he believes the girl’s name is Bella Bond, but doesn’t have that confirmed.

The Department of Children and Families opened a case file into Bella’s care by the Bond family in 2013, Baker said, and closed the case the same year. Baker says the family has no current involvement with DCF.

The child was found in a trash bag, wrapped in a zebra-striped fleece blanket. Investigators searched for her identity and parents for months. They executed a warrant on the apartment of Bella Bond’s family on Maxwell Street on yesterday Thursday. Boston Police Commissioner William Evans says his department received the tip that led officials to Maxwell Street.

Following Baker, House Speaker Robert DeLeo said officials told him last night Thursday night that they had a break in the case. He says the child’s mother was found in Lynn and is in custody.

DeLeo says officials have identified the mother's boyfriend as Michael McCarthy, who is at Beth Israel Hospital with “possible drug issues.” DeLeo says the mother and boyfriend are blaming each other “as to who harmed the child.”

He added that officials are taking witnesses in front of a grand jury.

State Police spokesman David Procopio says he cannot confirm any of the facts Baker and DeLeo related.

Rhonda Mann, a spokesperson for the Massachusetts Department of Children and Families, released the following statement:

— Rupa Shenoy

Update, 12:01: A law enforcement official says authorities have identified the girl who was found dead on a Boston Harbor beach this summer and whose case sparked a massive social media campaign to try to find out what happened to her.

The official spoke Friday on the condition of anonymity because he was not authorized to release details of the investigation. He said police searched a Boston home Thursday and have been in contact with family members.

A spokesman for the Suffolk district attorney's office said the investigation remains "very active." A state police spokesman did not immediately return calls.

The girl was named Baby Doe by investigators and was estimated to be 4 years old. Her body was found on Deer Island in Winthrop on June 25 by a woman walking a dog.

— The Associated Press

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Two local news outlets are reporting that Baby Doe has been identified and that an arrest has been made. The body of a girl believed to be around four years old was found along a rocky secluded coast of Deer island in late June.

For the intervening three months, the case has been a mystery.

Who and why would anyone leave a toddler's body in a garbage bag along with a little zebra blanket? And why has no one come forward?

Back in July forensic psychologist Robert Mendoza speculated that the child was likely local and that someone likely brought the baby’s body to Dee island in a vehicle - not by boat.

"I wouldn’t rule it out," said Mendoza, "it’s pretty tricky territory for weekend boaters.  So, I think it’s less likely, but in theory, that’s possible."

Today, the Suffolk County DA’s office says the investigation is still ongoing and are so-far not confirming reports that the child has been identified and an arrest made.

Winthrop police would not comment on the broadcast reports. They did, however, tell Tina Martin of WGBH News, that there is a major break in the case and they expected it to be resolved by day's end.

— Emily Rooney and Tina Martin