SAN JOSE PINULA, Guatemala (AFP) - Guatemala recoiled in anger and shock on Thursday (March 9) at the deaths of 33 teenage girls in a fire at a government-run shelter where staff have been accused of sexual abuse and other mistreatment.

The toll had climbed steadily from 19 killed in the Wednesday blaze itself, as 14 more girls succumbed in hospital overnight and Thursday to their horrific burns.

A dozen more survivors were said by hospital officials to be in critical condition.

All the victims were aged between 14 and 17.

They were all residents at the Virgin of the Assumption Safe Home for children just to the east of Guatemala City.

At the time of the tragedy, the decade-old facility, surrounded by a concrete wall and barbed wire, was hosting nearly 800 minors - double the number it was designed for.

An initial hypothesis by human rights prosecutors suggested teens in the centre started the blaze early on Wednesday by setting fire to mattresses during a lockdown, ordered after a group of more than a dozen children reportedly ran away on Tuesday.

An investigation is underway to determine the exact circumstances, and attribute criminal responsibility.

President Jimmy Morales fired the shelter's director. His government decreed three days of national mourning.

In a demonstration on Thursday, activists left dolls on piles of charcoal in front of Morales' presidential palace to decry perceived negligence by authorities.

Lucas Najera, a 76-year-old newspaper-seller and grandfather of a 14-year-old injured in the blaze, said: "They call it a 'safe home'. But how is it safe?"

"How is it they didn't realize in time to save them if the smoke was seen right away?" asked the uncle of one deceased 15-year-old at the capital's morgue. The man gave only his first name, Marvin. The charred remains of his niece were identified through a DNA sample.

Hilda Morales, a prosecutor defending children's rights who is not related to the President, called the fire "a massacre."

The head of the social welfare ministry in charge of the shelter, Carlos Rodas, said he took responsibility for what happened, but denied any failure of duty.

"We can't bring these lives back," he said. "But we can look at the system and make it more transparent."

President Morales said that before the fire, orders had been given to transfer some of the youths to other facilities because of the overcrowding.

Now, the centre's surviving children - including ones who escaped domestic violence, abandonment and living on the street, and former juvenile delinquents - were to be sent to various other state and private shelters.

Some were to be provisionally given to their families for care.

In recent years, complaints of alleged abuse against the Virgin of the Assumption Safe Home had accumulated.

Angel Cardenas, a former employee, said he had registered his own alerts while working there.

On Wednesday, outside the facility, he said the place "was a ticking time bomb - this (tragedy) was to be expected." Rosa Aguirre, a 22-year-old street vendor who rushed from the capital to see if her two sisters, aged 13 and 15, and her 17-year-old brother were among the casualties, said she, too, had lodged complaints.

She said brawls often broke out inside, and her brother was sometimes put in a dark isolation cell nicknamed the "chicken coop." She said she had tried in vain to gain custody of her siblings after their mother's death four months ago.

Dozens of children have run away from the home in the past year, reportedly to escape ill treatment.

Hilda Morales told reporters the centre's future was in question. She noted that last year the Inter-American Commission on Human Rights had found in favor of several adolescents who had alleged mistreatment and sexual abuse in the shelter.

Unicef, the UN children's fund, issued a statement stressing Guatemala's duty to investigate how and why the blaze started, and to compensate the victims.

It also criticised the systematic institutionalization of children and adolescents in the country, saying they "had the right to grow up in a family."

Resources in Guatemala, however, are inadequate. The country is the most populous of Central America, with 16 million inhabitants, more than half of whom live in poverty according to the World Bank.