The FSA says the individuals will be released on bail following questioning, but will not confirm any further details.
Yesterday it was announced that six men had been arrested in the first operation carried out jointly between the FSA and the Soca.
Sixteen addresses were searched in London, the South East and Oxfordshire and documents and computers were seized from residential and business premises.
According to reports, London-based hedge fund Moore Capital was one of the firms raided in the investigation and one arrest was made there.
It is believed that the city professionals passed inside information to traders (either directly or via middlemen) who traded based on this information and have made significant profits as a result.
The operation was carried out by 143 FSA personnel together with officers from Soca as part of a joint investigation that commenced in late 2007.