Previously, a 33-year-old British man - Robert Murat - was also declared "arguido" by detectives.

People given arguido/a status are officially treated as a suspect in a crime.

None of the three have been arrested or charged.

How is arguido status given and what does it mean?

Under Portuguese law either the police or a person being questioned can request that they be formally named as a suspect, a process called arguido.

Artur Rego, a Portuguese lawyer, told BBC News: "Arguido is the person who has been accused of being the perpetrator.

"This is just an accusation made exactly at the end of the investigation."

A person can ask for arguido status if they feel the line of questioning is implying that they are a suspect. This gives them more rights than a witness would have.

Artur Rego

What rights does an arguido have?

Arguido status gives a range of legal protections, such as the right to remain silent and the right to a lawyer during questioning.

Mr Rego said: "Sometimes when they [the police] suspect someone, they call that person in as a witness.

"They don't constitute him as arguido and they extract as much information from him as they can, because as a witness he cannot refuse to collaborate with the police.

"Now the moment he is constituted as arguido, as the defendant, then he can not only refuse to answer questions because they can incriminate him, but also he has the right to be accompanied in the questionings by his own solicitor."

Once someone is an arguido they can be arrested, but only if there is sufficient evidence.

What action can the courts take against an arguido?

The police can use their powers to bring the suspect before a judge to ask for restrictions to be imposed on their movements.

If they do, they could be banned from leaving their house or the area, or held in custody while the case continues.

In this case, the suspect is not subject to a judge's order, but has signed an identity and residence statement.