His younger brother Valentin, who also rode for Team Astana, was last month sacked from the team and banned for four years by the Kazakhstan Cycling Federation after admitting to a similar violation.
The positive test (PDF) came from a sample collected on 1 August, a day before Iglinskiy was due to finish the Clasica San Sebastian.
"In accordance with regulations of the MPCC to which the Astana team first adhered in 2013, the rider is suspended provisionally and shall remain out of competition in anticipation of the results from the B analysis," the team said in a statement.
The positive result has implications beyond that of the rider. As a
member of the Movement For Credible Cycling (MPCC), Astana could be
subject to a short suspension of its racing operations.
rules state (PDF) that if there are two positive tests in a 12 month period, a
team must remove itself from racing for eight days after notification of the violation,
with the suspension beginning on the first day of the next World Tour
race. If the rules are applied, Astana could miss this weekend's Giro di
Lombardia and later Tour of Beijing.
In his eighth year at Astana, Iglinskiy's biggest victory came at LiegeÃ¢â¬âBastogneÃ¢â¬âLiege, where he finished ahead of his now team mate Vincenzo Nibali.
Iglinskiy rode in support of 2014 Tour de France winner Nibali, finishing 129th, four hours and 22 minutes in arrears.
Astana team general manager Alexandr Vinokurov reacted angrily to the news, condemning the rider for letting down the country.
"All Astana Pro Team riders are contractually obliged to respect strict ethical rules and regulations," said Vinokurov.
"We will not tolerate any indulgences by any one entity, person or structure that violates these rules. I am very disappointed and angered that this rider could not have understood the basis of our rules and the importance of our ethics.
"It is especially unacceptable on the part of a Kazakh rider who stands for the image of our team and the image of our country."