AUCKLAND, New Zealand - Police searching for the mother of a 3-year-old girl whose father apparently abandoned her at a train station in Australia on Wednesday found a woman's body locked in the trunk of a car at the family's home in New Zealand.

The woman's body was not immediately identified, but the car was registered to the father of the toddler and the investigation into the whereabouts of the child's mother has now been upgraded from a missing person case to possible murder, said Detective Senior Sergeant Simon Scott.

Police in Australia, New Zealand and the United States as well as Interpol are looking for Xue Naiyin, a 54-year-old Chinese-language magazine publisher who aroused suspicion when authorities found his daughter, Qian Xun Xue, alone at a train station in the southern Australian city of Melbourne on Saturday.

Security video showed a man, believed by police to be Xue, accompanying the girl in the station then leaving her by an escalator. He boarded a flight to Los Angeles soon afterward, police said.

Father and daughter had travelled together to Melbourne from New Zealand last Thursday, and police said they held grave concerns for the girl's mother, Anan Liu, because she had not come forward after news broke that her daughter had been abandoned.

Scott told reporters Wednesday the body was found in a car registered to Xue outside the family home in the northern city of Auckland. A post mortem examination would be carried out Thursday to determine the woman's identity.

He said Liu was last seen about 10 days ago, and that the inquiry into her whereabouts was now a homicide investigation.

Meanwhile, Liu's mother in China was planning to travel to Melbourne to pick up her granddaughter, said Pansy Wong, a New Zealand legislator and ethnic Chinese community leader who spoke to the grandmother in China's Hunan province.

Qian Xun was born in New Zealand after her parents moved there in 2002.