A teenager has been arrested and accused of organising the murder of his 15-year-old girlfriend and their one-year-old daughter.

Police have been looking for the teenage mum and her baby daughter since 19th January when they went for a walk and vanished.

The investigation quickly pointed the finger of suspicion at her 16-year-old lover, who was also reportedly the father of the baby.

Police found that he had invited Amanda Madeira Lima and baby Maria Alice to go for a walk after meeting them together with his brother-in-law at their home in the district of Maristela in Brazil.

But after going to a rural area, around four kilometres from Maristela, they had slipped drugs into either her food or drink, and then set fire to her and her daughter using fuel purchased earlier from a petrol station.

The 16-year-old and his 30-year-old brother-in-law then buried the bodies.

But after being quizzed by cops, the teenager confessed what had happened, and also then named his brother-in-law, which led to the location of the bodies.

Local police chief Chief Lourenço Talamonte Netto said: “There is evidence that they [suspects] took fuel at a gas station and used it to set fire to the bodies. Including the packaging used to transport the fuel that was found at the scene.”

A post-mortem has now been carried out on the bodies of Amanda and Maria Alice in Botucatu.

The teenager is being detained at a youth facility while the older man is in investigative custody.

Prosecutors have not revealed the motive for the killing.