The operation took place at nine locations across the country involving the police, prosecutors, Swedish customs, as well as Sweden’s tax and debt collection agencies.

Around 300 officers and a large number of civil servants from the other agencies were involved in the raids.

Police carried out valuable seizures through a number of home searches, but a statement from the police doesn’t elaborate on what exactly was confiscated.

The raids have also been carried out with the aim of securing assets and property which was financed with proceeds from criminal activity.

The operations took place in Malmö, Gothenburg, Karlstad, Örebro, Eskilstuna, Stockholm, Sollefteå, Örnsköldsvik and Umeå.

According to police, the raids in Karlstad, Örebro and Umeå were especially important.

The raids are the product of an investigation which began with the discovery of a package at Stockholm’s Arlanda airport back in May.

A customs agent discovered that the parcel contained large quantities of growth hormones.

Arlanda has been shown to be a major point of entry in Sweden for performance enhancing substances, and most of the materials confiscated by Swedish customs have been recovered during checks of post and parcel items passing through the airport.

The May find at Arlanda was handed over to narcotics police in Sundsvall in northern Sweden, who launched an investigation which later included assistance from the Swedish Customs Agency (Tullverket) and the National Criminal Investigative Department (Rikskriminalpolisen).

During the summer, the investigation grew and in September other police departments from around the country were brought into the probe.

The investigation has so far revealed the existence of a well-organized and wide-ranging trade in doping substances across the whole of Sweden, involving large sums of money.

Of the 40 people arrested, approximately 10 reside in Örebro County in central Sweden.

“They were born between 1946 and 1986. One of them is a woman,” Örebro police spokesperson Torbjörn Carlson told the TT news agency.

He said that one of the people arrested in Örebro has previously been sentenced for drugs related offences and other related crimes.

“Otherwise we don’t have records on any of them,” said Carlson.

Carlson can’t say how much doping material was confiscated in the Örebro raids, but described it as a very comprehensive raid.

The Wednesday morning raids were called Operation Liquid and took place, according to police, within the framework of a government mandate to fight serious organized crime.