In a particularly horrifying murder, a 2-year-old who was being toilet-trained was beaten until his bones were broken and his liver was crushed, and then was left to languish for hours without medical care until he finally died, it was charged yesterday.

The mother of the boy and her roommate are accused of beating the child to death at their Morningside Heights housing project.

Zahira Matos, 20, the mother, and Carmen Molina, 32, were charged with second-degree murder, endangering the welfare of a child, and second-degree assault in the death of Yiovanni Matos on Sunday morning at the Grant Houses, located at Broadway near 125th Street.

At Ms. Matos’s arraignment late yesterday in Manhattan Criminal Court, Judge Patricia Nunez ordered held without bail. At that, Ms. Matos placed her head in her hands and appeared to be weeping. Her lawyer, Samuel Leibowitz, declined to speak to the press.

Ms. Molina was to be arraigned later last night.

The cause of death was multiple blunt impact injuries to the head, torso and extremities, along with fractured ribs and extremities and a lacerated liver, according to Ellen Borakove, spokeswoman for the medical examiner. The manner of death was ruled fatal child abuse syndrome, and prosecutors said the boy had 60 bruises on his body.

Prosecutors alleged the defendants acknowledged periodically beating the child with their hands and whipping him with a belt. “The defendant admitted that the child was beaten frequently in connection with potty training,” an assistant district attorney, Dan Robinson, told Judge Nunez.

According to prosecutors, Ms. Molina said she punched Yiovanni repeatedly Saturday, until his leg was in a distorted position, and then she left him unattended in the bathroom. “Defendant Matos did not remove the child from harm and left the child with defendant Molina,” Mr. Robinson told the court.

At 2 a.m. Sunday, police officers and EMS workers went to the defendants’ apartment at 3170 Broadway, responding to a report of an unconscious child. The boy was taken to St. Luke’s Hospital, where he was pronounced dead at 2:26 a.m.

Ms. Matos’s two daughters – a 3 1 /2-year-old girl and a 2-month-old baby – were in the apartment at the time of the alleged abuse, prosecutors said. According to a neighbor, Ms. Molina has three children but only Ms. Matos’s children lived at the apartment.

As a police officer stood guard outside the empty apartment yesterday afternoon, neighbors at 3170 Broadway spoke of Ms. Matos and Ms. Molina.

“[I’m] surprised to hear about it,” said Jose Cavrera, 39. “As far as I know, she’s a good mother. As far as I know, she didn’t have any problems.[The children] seemed well-dressed and taken care of.”

Lisi de Bourbon, spokeswoman for Administration for Children’s Services, said Ms. Matos’s two surviving children were placed in foster care following the murder, but ACS had no prior involvement with the family.

Ms. Matos and Ms. Molina had just moved into the apartment this summer and were not well-known to other residents of the 15th floor. They would pass them in the hall or ride with them on the elevator and exchange greetings, and sounds of crying were dismissed as normal.

“I heard the baby crying, but I thought it was for milk, not for anything out of the ordinary,” Mr. Cavrera said. “They were being disciplined, I thought. Nothing like child abuse.”

Another neighbor, who declined to give her name, said she usually kept her television too loud to hear outside noise, but on Saturday night she heard screaming, which she quickly dismissed.

“Nobody on this floor really knew the two girls,” said the neighbor, who has lived there 18 years. “They just moved onto this floor. That night I heard screaming. That was all.”

Iris Matos, sister of the defendant, lived at the apartment for eight years and was well-known to her neighbors. But Mr. Cavrera, who said he has lived at his Grant Houses apartment since 1979, said Iris Matos did not stay there for long once her sister moved in this summer with her three children and Ms. Molina.

“[Iris] told me that her sister was living with her and she wasn’t happy about it,” said Mr. Cavrera.

Police said that Ms. Matos had no prior arrest record and that Ms. Molina had no violent past. Ms. Molina was arrested in August for petty larceny, police said, and in 1998 at Elmhurst, Queens, for filing a false report. The disposition of those cases was not clear.

The two women’s arraignment came the same day as the arraignment of a Brooklyn man, William Lee, whose 3-year-old son’s body was found in a gym bag outside a church in Queens.

William Lee pleaded not guilty to charges of endangering the welfare of a child, reckless endangerment and improper disposal of a body. He is being held on $100,000 bail.

Mr. Lee allegedly kidnapped Marcus Lee on Wednesday and, when he surrendered to police Friday, allegedly said he dumped the boy’s body in Jamaica.

No homicide charges have been filed in the case because the medical examiner’s office has not yet established the cause of death.