The eldest son of Norwegian Crown Princess Mette-Marit has been released from custody after his arrest last week on rape allegations, his lawyer said.

Marius Borg Hoiby, 27, is the stepson of the heir to the Norwegian throne, Crown Prince Haakon, and the son of Ms Mette-Marit from a previous relationship. He has no royal title or official duties.

Borg Hoiby was arrested last week in Oslo on a preliminary charge of having had “sexual intercourse with someone who is unconscious or for other reasons unable to resist the act”, police said.

In Norway, a preliminary charge comes before a formal charge and allows authorities to detain suspects during an investigation.

At the time, the authorities did not say when the alleged rape occurred. Norwegian media reported that Borg Hoiby denied the accusation.

Prosecutor Andreas Kruszewski said on Wednesday that police had reviewed the evidence seized in connection with Borg Hoiby’s arrest and had conducted witness interviews.

Oslo police said in a statement that the decision was taken not to seek the further detention of Borg Hoiby.

“As of now, we can no longer see that there is a risk of evidence being tampered with,” it said.

The statement added that a police investigation has been launched into “a further matter relating to sexual offences”, without giving details of that case.

Oyvind Bratlien, Borg Hoiby’s defence lawyer, said his client’s release was “not surprising”.

“He shouldn’t have been imprisoned at all,” Mr Bratlien told broadcaster NRK. He later confirmed to Norwegian news agency NTB that his client had been released.

The royal palace had no comment regarding the allegations against Borg Hoiby, NTB said.

Borg Hoiby lives with the royal couple and their two children, Princess Ingrid Alexandra and Prince Sverre Magnus.