Police arrested Hickey, the president of the Olympic Council of Ireland (OCI), and of the European Olympic Committees, early Wednesday at a hotel in Barra da Tijuca, where the Rio Games' Olympic Park is located, reports Efe.
The 71-year-old Hickey felt ill after being arrested and was taken to a hospital but is to be taken to a police station for questioning.
Police said they were also looking for seven other suspects, including a British man and several Irish citizens.
OCI hired the company Pro10 Sports Management as its Authorised Ticket Reseller (ATR), for the Rio Olympics, but some of those OCI-allocated tickets ended up in the hands of the firm THG Sports, which is controlled by English businessman Marcus Evans.
Arrest warrants were issued this week for Evans and three other THG executives, the Rio de Janeiro daily O Globo reported.
THG was the OCI's authorised reseller for the 2012 Olympics in London but was not its ATR for the Rio Games.
THG allegedly illegally sold tickets for the August 5 opening ceremony for $8,000 apiece, several times more than the highest official price.
IOC spokesman Mark Adams said in a statement on Wednesday that the committee was waiting to learn the precise charges filed against Hickey and trying to establish the facts of the case, adding that like any suspect he must be presumed innocent until proven otherwise.
Police have not yet asked IOC for information, according to the spokesman, who confirmed that the Irish Olympic committee had allegedly sold 1,000 tickets illegally.
Adams tried to put the accusations into perspective when asked if the distribution of tickets by national Olympic committees fuelled corruption, noting that the case involved 1,000 OCI-allocated tickets out of a total of 6.5 million tickets available for purchase for the Rio Olympics.
