Alaver was detained, the prosecutor's office told ERR, first at his home in Tartu and then taken to a Police and Border Guard Board (PPA) station for further questioning, without commenting to ERR's Madis Hindre (see video clip below).

Alaver was subsequently released by the PPA on Monday evening in accordance with procedural steps, and allowed to return home, without being formally arrested (the prosecutor's office would have needed to apply to the courts for Alaver's placing in custody).

The investigation concerns possible criminal activity beginning in 2016 and which involved influencing Estonian skiers in the use of blood doping.

''It is not possible to state at this point in time who may or may not have been influenced into engaging in doping activities, said leading public prosecutor Taavi Pern.

Mr Pern added that his counterparts in Austria and Germany have given an adequate overview of exactly what crimes are being investigated in those countries.

''From the information we have received from our Austrian and German partners, we now know that they are engaged in extensive criminal proceedings. However, there is at the same time a lot of new public information which makes it rational to initiate separate criminal proceedings in Estonia,'' said Mr Pern on Monday.

Separate proceedings in Germany and Austria continue

Mr Pern added that criminal proceedings in Austria as to possible doping use by the skiers is to continue.

''According to information available to us concerning the criminal proceedings initiated by the Austrian public prosecutor's office, amongst other things, the circumstances related to the use of doping by several athletes has been clarified,'' he went on.

Criminal proceedings have been initiated pursuant to § 195 of the Estonian Penal Code, which entails either a financial penalty, or up to three years' imprisonment for repeatedly inciting doping activities; proceedings are conducted by the Central Criminal Police, under the direction of the Public Prosecutor's Office.

Ski coach and former head of Estonia's skiing governing body Mati Alaver is also the subject of an investigation into a potential international doping ring, according to German investigative journalist Hajo Seppelt.

Alaver also subject of German investigative journalist

Mr Seppelt has long been involved in investigative work into doping activities in his native Germany, in Russia, and in other countries, principally for the Arbeitsgemeinschaft der öffentlich-rechtlichen Rundfunkanstalten der Bundesrepublik Deutschland (ARD), Germany's federal association of its regional public broadcasters.

In a tweet (see below), Mr Seppelt said that: ''According to information available to German public broadcaster ARD's doping desk, an international police search is ongoing for Estonian Mati Alaver in connection with the Erfurt affair. Alaver is suspected of having been one of the key figures, and according to some sources might even have been the "general", a code name given to one of the organisers of the crime ring''.

Nach Informationen der ARD-Dopingredaktion läuft internationale polizeiliche Fahndung gegen Esten Matti Alaver im Zusammenhang mit Erfurt-Affäre. Verdacht: war eine der Schlüsselfiguren. Eingeweihte sagen: er war womöglich der "General" - interner Code für einen der Drahtzieher

— Hajo Seppelt (@hajoseppelt) March 11, 2019

Erfurt, Germany, is where Doctor Mark Schmidt, thought to have been at the centre of many sports doping activities and arrested at the same time as two Estonian skiers, Andreas Veerpalu and Karel Tammjärv, as well as a Kazakh skier and two Austrian skiers, on Wednesday, 27 February at the world championships in Seefeld, Austria.

Alaver's name recurred in conjunction with German ''doping doctor''

Following the arrests and revelations, Alaver was stripped of his position with the ski authority, as well as state awards conferred to him during the presidency of Arnold Rüütel, membership of the Reform Party, sponsorship by various companies, plus other forfeitures.

He told ERR at the beginning of March that he had been in contact with Mark Schmidt, but at the same time rejected charges that he supported blood doping.

One of the two Estonian skiers arrested, Tammjärv, stated that it was Alaver who had put him in touch with Schmidt in the first place, in 2016.

One of the skiers son of olympic ski star

Alaver has also repeatedly denied that Andrus Veerpalu, three-times nordic skiing olympic medallist and father of Andreas, had anything to do with the doping activities. Veerpalu senior had strong connections both with Alaver, Team Haanja - the two arrested skiers' team, and the Kazakh skier,Alexey Poltoranin, also arrested by Austrian police.

''We are studying this information; there is nothing more to say now," Olja Kivistik, spokesperson for the State Prosecutor's Office, told ERR, prior to the prosecutor's office announcement that it would be initiating proceedings.

After being released from detention on the evening of Thursday, 28 February, Karel Tammjärv gave a press conference (on the Friday) together with coach Anti Saarepuu, apologising for his actions. Andrus and Andreas Veerpalu skipped the conference and returned to Estonia without making comment; Andreas Veerpalu later made a statement via his mother, extending his apologies as well.

Marko Pilv appointed Alaver lawyer

Another skier, Algo Kärp, came forward last week and admitted to being involved in blood doping, after being given the contacts for Mark Schmidt, again by Alaver.

Alaver is to be legally represented by sworn advocate Marko Pilv.

Mr Pilv told the media on Monday afternoon that Alaver's PPA interrogation was concluded, but that he couldn't comment further.

He could also not comment neither on whether Alaver had committed a crime, nor what Alaver's reaction to the accusations was, nor any message Alaver might have for the Estonian public.

Whilst the prosecutor's office has said it is not seeking permission to arrest Alaver from the courts, Mr Pilv could also not comment on when Alaver might be released from detention.

Mr Pilv is son of senior advocate Aivar Pilv, who represented Andrus Veerpalu, father of one of the Estonian skiers, Andreas Veerpalu, allegedly involved in doping activities. Following accusations of doping in 2011, Andrus Veerpalu was subsequently cleared by an international sports arbitration court, in 2013.