A 3-year-old boy found dead Tuesday morning in a Southeast Washington apartment was beaten, according to D.C police, who said on Thursday that the death has been ruled a homicide by blunt-force trauma.

Authorities identified the child as Xavier Lyles of Southeast. A search warrant application filed in D.C. Superior Court says paramedics noticed bruising on the boy’s body. Authorities did not comment on whether a suspect has been identified.

Police said they were called about 11:10 a.m. Tuesday to the fourth-floor apartment where the boy lived with his sister and mother in the 2500 block of Pomeroy Road SE. The emergency call was for a child not breathing.

The boy’s mother told police that her son had no health problems and that she had put him in his sister’s bed about 5:30 p.m. on Monday, according to the search warrant. That document says the mother reported that she checked on Xavier at 8 that night and that he “opened his eyes and went back to sleep.”

About 10 a.m. Wednesday, police said in the warrant application, Xavier’s 9-year-old sister found that her brother had vomited and was unresponsive. Police said the mother called her cousin, then 911. Paramedics pronounced Xavier dead at the scene and the body was taken to the medical examiner’s office for an autopsy.

Police said they interviewed family members and other witnesses and concluded that the child had been beaten. Police would not comment further. Relatives, including Xavier’s mother, could not be reached for comment over the past two days.

Neighbors said the victim’s mother had lived at the apartment for about a year but didn’t interact much with other tenants. Police said in the search warrant document that detectives seized as evidence a fitted sheet, a matching pillowcase and a colored pillowcase.

Xavier is the third child whose death was ruled a homicide in the District this year. The children in the other two cases died in 2013, but those cases were not immediately determined to be homicides.

In one, a 31-year-old woman was charged with felony murder after authorities alleged that she fed her month-old son, Hakeem Brown, a fatal dose of a prescription allergy and motion sickness medication. The woman told police she gave the infant the ground-up pill because he was being fussy about eating, according to court documents. Tisheena Louise Brown of Southeast pleaded guilty to voluntary manslaughter and is scheduled to be sentenced July 18.

In another, a 21-year-old woman was charged with killing her newborn son in the bathtub of her family’s Northwest Washington apartment. Lillian Alvarado told police that her baby — who was never named — had been born dead, but police said the death was ruled a homicide by asphyxiation and dismemberment. Alvarado, charged with first-degree murder, has a hearing on her mental status scheduled for July 24.

There were three infants or young children slain in the District in 2013.

Jennifer Jenkins contributed to this report.