the cause of the fire
Se desconocía la causa del incendio.
The cause of the fire was unknown.
No se sabe la causa del incendio.
The cause of the fire is unknown.
Se sabía la causa del incendio.
The cause of the fire was known.
La causa del incendio es desconocida.
The cause of the fire is unknown.
Se desconoce la causa del incendio.
The cause of the fire is unknown.
No se conoce la causa del incendio.
The cause of the fire is unknown.
La causa del incendio era desconocida.
The cause of the fire was unknown.