A missing newborn has been found alive and her mother has been found dead in the boot of a car 160 miles from where they disappeared.

Heidi Broussard and her three-week-old daughter had last been seen in Austin, Texas, on 12 December, when she dropped her six-year-old son off at school at around 7.30am.

Police have said the mother and her baby, named Margot, were found at a house in Houston on Thursday.

The three-week-old infant is said to be in 'very good health'. Pic: NBC News
Image: The three-week-old infant is said to be in ‘very good health’. Pic: NBC News

The infant – said to be in “very good health” – was inside the building and is in the care of child protection services.

DNA testing is underway to confirm her identity, but authorities said her looks are “consistent” with the missing baby’s.

NBC News reports that a post mortem is being carried out on Ms Broussard’s body, whose cause of death is said to have been recorded as strangulation.

Police arrested her friend, Megan Fieramusca, after raiding her home.

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She has been charged with two counts of kidnapping and one of tampering with a corpse.

According to her family, Ms Broussard was found in the boot of a car at the property in Houston, which is more than three hours from Austin by road.

Megan Fieramusca has been arrested and charged. Pic: NBC News
Image: Megan Fieramusca has been arrested and charged. Pic: NBC News

Her mother Tammy Broussard told NBC News that police told her about the discovery, with the family left baffled by the sudden disappearance of the 33-year-old.

Heidi Broussard’s boyfriend and Margot’s father Shane Carey said earlier in the week that her car and belongings, including her identification and baby supplies, were still at her Austin apartment the day she disappeared.

Friends had told NBC News there is “no chance” she would have left of her own accord without her son.