Mexican prosecutors have formally charged eight people in the grisly cult killings of two 10-year-old boys and a 55-year-old woman.

A fast-moving fire killed 31 children in a day care centre in northern Mexico, despite desperate attempts of firefighters who punched through the walls and fought their way through flames to rescue babies, toddlers and others trapped inside.

Flames engulfed a day care centre in the northern Mexican city of Hermosillo, killing at least 29 children and sending dozens more the hospital.