The man, who was arrested on Wednesday afternoon, is 21 years old and comes from a northern area of Stockholm. According to his lawyer, the suspect denies any crime.
He is suspected of involvement in the heist, during which two 17th-century royal crowns were taken from a cathedral in Strängnäs, one hour from Stockholm, where they had been kept in a locked and alarmed display case.
The 21-year-old has been arrested “on probable cause” (the higher degree of suspicion according to Swedish law) of aggravated theft.
According to the Swedish Prosecution Authority, the jewels, stolen on July 31st this year, have still not been found.
Two suspects were at the time seen fleeing from the scene on women's bicycles and then a motorboat, and police carried out searches by water and air. A police spokesperson told told The Local in early August that the forensic team had found “traces” both in and outside the church, but said it was too early to say what kind of evidence these might be.
The crowns were made for the burial of Kind Charles IX and his wife Christina, and date back to the early 1600s. The gold jewels are decorated with silver and pearls, and a royal orb was stolen as well.
July's royal heist was the second to take place in the area around Lake Mälaren in recent years.
In 2013, a crown and sceptre used in the funeral of Sweden's King Johan III were stolen from nearby Västerås. Those items were later located in two large rubbish bags at the side of a highway following a tip-off to police.