YOKOSUKA NAVAL BASE, Japan — Investigators looking into the deaths last week of a Navy wife and her newborn daughter say the baby died from trauma and that the mother’s death is being investigated as a suicide, according to Yokosuka city police.

Kaoru Stout, the Japanese-born wife of a USS Gary sailor, died Sept. 16 after plunging nine stories from the Jyuban Tower apartments. Stout and her husband, Petty Officer 1st Class Ehron Stout, lived in a ninth-floor apartment with their newborn baby.

The 33-year-old woman died the morning after her baby was pronounced dead at Yokosuka Kyosai Hospital on Sept. 15.

“We believe the cause of the baby’s death is not from sickness,” said a Yokosuka city police spokesman, speaking on the customary condition of anonymity. The spokesman said authorities had not yet determined exactly how the 2-month-old infant had sustained the injuries or whether the trauma was intentional or accidental. The spokesman said authorities still were investigating whether the baby had been “dropped or hit” or injured in some other way. The baby’s name was not available.

The spokesman said they believed the mother’s fall, around 6:30 a.m., was intentional. Although an accident or even homicide wasn’t being completely ruled out, the spokesman said, those possibilities were believed to be far less likely. He said no one witnessed the woman’s fall.

Her husband, also 33, is not a suspect in the case, said Mike Chase, Yokosuka base spokesman.

Japanese police are involved in the case because the woman was a Japanese citizen. However, the police said, the Naval Criminal Investigative Service was taking the lead on the case, with Japanese authorities acting as “an adviser.”

Chase declined to comment on the investigation or confirm the Japanese spokesman’s account but said last week that U.S. and Japanese authorities were “working together closely” on the case.

The NCIS special agent in charge could not be reached for comment. According to the NCIS Web site, “the public cannot obtain information on pending NCIS investigations.”

Stars and Stripes independently confirmed the names of the couple. Navy public affairs officials refused to identify them, citing concerns about possible “harm or embarrassment,” and said the names would be made public only after investigations into the deaths were completed a month or more in the future.

The woman was pronounced dead at the base hospital at 7:13 a.m. Sept. 16, Chase said. The morning before, her infant daughter had been taken to the base hospital, but doctors there determined the baby needed care they couldn’t provide, Chase said, so the infant was taken to Yokosuka Kyosai Hospital nearby.

The base hospital does not have an intensive care unit for newborn babies; Yokosuka Kyosai Hospital does.

Chase said the baby died at the Japanese hospital shortly after noon and then was returned to the base hospital’s morgue.

Neighbors of the Stouts said both Japanese and NCIS investigators were working in the couple’s apartment and common hallway from about 3 p.m. to 11 p.m. the day the baby died.

Chase declined to answer how Kaoru Stout came to be at the apartment early Sept. 16 or say whether she was alone. He declined to say where her husband was at the time of the baby’s injury or the time of his wife’s death.

The woman was discovered by a passer-by, according to Chase.

In addition to the criminal investigation, a legal investigation also is initiated when a death occurs, said Cmdr. John Wallach, spokesman for Commander Naval Forces Japan. That investigation includes findings of fact and opinion, and, if determined, recommendations.

It’s unknown how long Ehron Stout has been assigned in Japan or how long the couple was married. Kaoru Stout reportedly had a son of about 4 years old from a previous marriage. Records show that the petty officer had at least one previous tour at the base, where he was assigned to a shore command.

A memorial was scheduled on Sept. 24 at an off-base location near the main gate. But Capt. Samuel Perez Jr., commodore of Destroyer Squadron 15, said the ceremony was not for the public. “Petty Officer Stout has requested this be for family and friends,” Perez said.