(CNN) -- A sixth baby has died nearly a month after a fire in the intensive care unit at Giulesti Maternity Hospital in Bucharest, Romania, officials said Sunday.
The premature baby, who was 14 days old at the time of the August 16 fire, suffered severe burns over more than 50 percent of his body and also serious burns of the airways, but he survived for 27 days. He died Sunday.
Three babies died in the fire, while two others succumbed in the following days.
Five babies remained in stable condition at Grigore Alexandrescu Hospital and have started to gain weight, said hospital official Dr. Dan Enescu. Although doctors are optimistic about the babies' prognosis, Enescu said, physicians still must wait until the infants are stronger before performing any surgeries.
Three people have been charged, one of whom was placed under arrest.
Florentina Cirstea, a nurse in charge of the maternity hospital's intensive care unit, was ordered held for 29 days last month while officials continue their criminal investigation. She is accused of manslaughter and unintentionally causing injuries.
The other two suspects -- the hospital's chief of the technical department and the head of the neonatology department -- also face negligence charges but remained free Monday.
Authorities say Vasile Dima, the technical department chief, didn't fulfill his duties because he didn't make sure the operation in his department ran smoothly and didn't take steps to prevent fires even though he was also in charge of the hospital's civilian firefighting team.
In the investigation after the blaze, authorities found violations of safety rules involving workers, the security of electrical systems and human resources management, said Marius Iacob, the chief prosecutor in charge of the probe.
The hospital faces charges of manslaughter and unintentionally causing injuries, Iacob said.
Cirstea's colleagues at the hospital sent a letter to media outlets last month expressing their support for her and blaming the Romanian health care system for the tragedy.
During her 14 years as a nurse in the intensive care unit, the letter said, Cirstea has taken care of thousands of premature babies with health problems. She has saved many of those babies through her professionalism, the staffers said in the letter.
The judge accepted the prosecutors' request to arrest Cirstea because she failed to fulfill her duties to care for the 11 newborns in the intensive care unit at the time of the blaze.
Besides those allegations, the judge noted in the motivation for deciding to arrest Cirstea that she changed her statements and lied several times about what she was doing and why she left the ICU.
When she was supposed to have been on duty in the ICU, Cirstea left the newborns unattended for 12 minutes, going to another hospital room and to the bathroom, the prosecutor said in the arrest warrant.
A defense lawyer acknowledged that her client left the ICU to go to the bathroom, but said she then was called by a colleague to another room because the colleague had been called to help deliver a baby.
Parvu said Cirstea deeply regrets what happened, but also blamed the health care system. Cirstea's job description said that at least two other nurses were supposed to be with her in the unit at all times, but she was alone, the attorney said.
If convicted of manslaughter, Cirstea could be sentenced to up to seven years in prison.