All 27 people arrested in connection with the police investigation into allegations of race-fixing have had their bail extended until October.
A City of London Police spokesman said: "This is a complex investigation and there are likely to be more arrests.
"To accommodate that and to go through the 2,500 listed exhibits, which include a large number of mobile phones and computers, and with still a significant number of races to look at, the decision was taken to extend the bail until October."
Sixteen people, including jockeys Kieren Fallon, Fergal Lynch and
Darren Williams, and trainer Karl Burke, were arrested and bailed in September.
Since then, a further 11 people have been questioned and bailed.
None of those arrested has been charged with any offence.