A massive search effort is underway for a young woman who mysteriously vanished outside her Texas home on Christmas Eve, with law enforcement officials saying she could be in "imminent danger".

Camila Mendoza Olmos, 19, was last seen leaving her home in Bexar County, Texas the morning of 24 December, according to the Bexar County Sheriff's office.

She normally goes on a morning walk, but her mother became concerned when she did not come home at a reasonable time, the sheriff's office said.

Sheriff Javier Salazar told ABC News that authorities believe she is in danger and are not ruling out kidnapping or trafficking. They are also considering that the case may cross international borders.

But, he added, Mendoza Olmos may have left on her own accord.