The seven suspects, including the former chairmen of Diyarbakırspor and Giresunspor, were sent to Metris jail in Istanbul overnight.
They are among 61 people, including the chairman of champions Fenerbahçe, detained since Sunday in a probe which has hit soccer company shares and thrown preparations for next season into disarray a month before kickoff.

Prime Minister Tayyip Erdoğan, himself a Fenerbahçe fan, called for a rapid and just outcome to the investigation, saying the affair was staining the country's image internationally.
"Let's not be stained in the international community. In fact the current discussions (of the investigation) are already a stain. This must be cleaned up rapidly," he told reporters at a news conference to announce his new cabinet.
The Istanbul court released another 11 people, whom prosecutors had asked to be remanded in custody, bringing the total of those released to 15.
Prosecutors on Wednesday were questioning another 25 suspects, including two Fenerbahçe directors, two Fenerbahce players and the chairman of Sivasspor, Anatolian said.
On Tuesday, Turkey's football federation said it would act swiftly in response to the allegations, without waiting for the outcome of the judicial investigation.
HEART PROBLEMS
Fenerbahçe, which is at the centre of the probe and whose chairman Aziz Yildirim is the highest-profile detainee, won the league for a record 18th time last season to qualify for the Champions League along with second-placed Trabzonspor.
If any clubs are found guilty of wrongdoing they could face exclusion from competitions, relegation to a lower division and the loss of potentially tens of millions of dollars in income.
Any individuals convicted of crimes could also face lengthy prison sentences.
Fenerbahce's Yıldırım was receiving hospital treatment on Wednesday for suspected heart problems.
European soccer governing body UEFA has set a deadline of July 15 for confirmation of the team taking part in the third Champions League qualifying round.
Police launched raids in 15 provinces across Turkey on Sunday, searching club premises and detaining players and administrators in connection with the scandal.
Turkish media have cited allegations in police reports such as a striker being offered money to not score in one game, a goalkeeper deliberately failing to prevent a goal and a club requesting a particular referee for a key derby.
Shares in the listed company of Istanbul-based Fenerbahçe have lost a third of their value since news of the investigation emerged. Other clubs have also suffered share price falls.
Fenerbahçe said in a statement it had not been involved in any wrongdoing and expressed its faith in the justice system.
Among matches being investigated were two Fenerbahçe games, both of which the club won, against Eskişehirspor and Sivasspor last season.