The photo has been used for illustrative purposes only.
Social services removed the girl from her family home in the town of Eberswalde, north of Berlin, and transferred her to a hospital on Dec.20.
She has since been released and is now in state care, as are her two older siblings.
The local "Maerkische Oderzeitung" daily reported at the weekend that the girl appeared to have suffered "extreme neglect" and was physically and mentally behind in her development.
"She reportedly saw no daylight for several years and was left to fend for herself for at least the last two years," national news agency DPA reported.
The public prosecutor's office in Frankfurt on the Oder said it had opened a probe against persons unknown on suspicion of child abuse.
Daniel Kurth, the head of the Barnim district authority where the family lives, told reporters on Monday that the girl "had not received the care and love of her parents that she needed," citing signs of malnutrition and speech issues.
There are no indications the girl's siblings suffered similar neglect, another local official told the same press conference.
The case prompted outrage in Germany, with the topselling Bild daily asking why the youth welfare office did not inform police even after deciding the girl's situation had deteriorated enough to remove her from the home.
According to Kurth, youth welfare workers had been in touch with the family since 2017.
The case recalls that of another girl, Jennifer, who was 13 when it emerged in 2009 that her parents had hidden their developmentally disabled daughter from the outside world for years.
Her family lived in the same German state of Brandenburg.
Mostly Muslim Gambia launched a lawsuit in November at the United Nations' highest body for disputes between states, accusing Myanmar of genocide against Rohingya in violation of a 1948 convention.
The Public Safety Act (PSA) was a "lawless law" under which the authorities hold children, old people and the disabled, and it should be scrapped, the group said.
UN chief Antonio Guterres denounced the "horrendous" attack and demanded an independent investigation, as a divided Security Council failed to condemn the strike.
"I salute you, mothers of martyrs, whose sacrifices show your great attributes and sincere patriotism. You are an honourable example for us and all other mothers to follow. Your sons lost their lives in the battlefields while defending their nation..."
Even as China opened to the outside, Jiang’s government stamped out dissent at home. It jailed human rights, labor and pro-democracy activists and banned the Falun Gong spiritual movement, which it viewed as a threat to the Communist Party’s monopoly on power.
The Darb toll gate system will be free of charge during the holiday starting from Thursday, December 1, 2022 and will be reactivated on Monday, December 5, 2022 during the regular peak hours (from 07:00 am to 09:00 am and from 5:00 pm to 7:00 pm).