Who is she? The computer generated image of Baby Doe. Source: Supplied

Inside was the decomposing body of a small girl. Wrapped in a zebra-print blanket and dressed in polka dot leggings, there were no other clues about who she was, or how she came to be dumped on Deer Island in Boston Harbour.

So begins the mystery of Baby Doe.

Without a name, that’s what police christened her, immediately appealing for public help. But it wasn’t until they issued an extraordinary computer-generated image of what Baby Doe would have looked like that her tragic story came to life.

Something about the girl staring back, her chubby cheeks and expressive brown eyes, caught the imagination, jarring with the cold reality of her little body stuffed in a bag and discarded like rubbish near a wastewater treatment plant.

Her picture quickly ricocheted around the internet, shared tens of millions of times along with the same sorry lament: ‘Who could have done this?’

Baby Doe was found on June 25 but police won’t say how long she may have been dead by the time she was found, whether she washed up on the beach or was dumped there. They have put her age at about four.

Her picture was first posted to the Massachusetts State Police Facebook page and shared 45 million times.

But still no-one has come forward with a name.

The leggings that Baby Doe was wearing are sold at Target. Source: Supplied

The blanket that was found in the rubbish bag with Baby Doe’s remains. Police say it might have been “special to her”. Source: Supplied

Authorities have vowed they will not rest until the case is solved.

Bob Lowery, the vice president of the Missing Children Division, told the Washington Post composite images like the one created for Baby Doe could be the key to uncovering what happened to her.

“It’s the public we need to engage with, to look at this child, because that’s how we’re going to get her identified,” he said.

“Every now and then we have a case like this, and that probably has a lot to do with the age of the child, the circumstances in which the child was found. Sometimes it touches the hearts of many and it motivates the public to get motivated to help.”

And without it all they have are the cold, physical facts. Baby Doe was almost 14kg and just over a metre tall.

“It has by far shattered our previous record for Facebook views,” said Jake Wark, a spokesman for Suffolk County District Attorney Daniel Conley, told Fox News.

Investigators still don’t know how she died after a post mortem failed to establish a cause of death. There were no obvious signs of trauma and toxicology tests that will hopefully determine if she was poisoned or ingested drugs.

It’s not as if the public haven’t tried to be helpful. Dozens of tips have been received which led to checks on as many as 20 possibilities. But each one turned out to false.

Authorities don’t even know if the girl’s death was an accident or a crime.

During a news conference on Tuesday, Mr Conley appealed directly to the girl’s parents

“Please step forward, clear your conscience and help us identify this young child,” he told them.

“She deserves to have her identity known to the public and she deserves the kind of dignified burial of any human being.”

Meanwhile, ordinary people from all over the United States and even as far Canada and Puerto Rico have shared the posting. Their messages range from sadness to anger.

“How can someone just throw a child away?” wrote one woman from Arizona. “This is just horrible, no one is missing this little angel!” wrote another woman from Clovis, California.

According to Fox, State police spokesman David Procopio said investigators are grateful to the public for “caring about this little innocent.”

“But we continue our request for leads,” he said.

“We need people to continue to look at her and think about her and let us know if anything in their memory clicks.”