John Welsh, David Buchanan, Keith Keane, Bailey Wright, Graham Cummins and Ben Davies, together with Barnsley’s Stephen Dawson, were questioned by officers from the National Crime Agency.
Six other people who were originally held in December over spot-fixing claims - prompted by information passed on by the Sun on Sunday newspaper - were re-arrested on Thursday.
Welsh, Buchanan, Keane and Wright are first-team regulars and look set to be included in North End’s squad for Saturday’s game against Bristol City at Ashton Gate.
Cummins has been on loan at Rochdale since September, while Davies is on a season-long youth loan with York City.
North End had released a statement on Thursday afternoon confirming that the club had been contacted by the National Crime Agency.
The statement read: “In response to media inquiries received, Preston North End Football Club can confirm that today, April 3 2014, the club has been contacted by the National Crime Agency in relation to a wide-ranging investigation into ‘spot fixing’ in football.
“There are no suggestions that any offences that might have occurred involved match-fixing.
“None of our employees have been charged with any offence at this time and until or unless this position changes we will be taking no further action nor making any further comment.
“All of our contracted employees are available for selection by the manager.”
A Football League spokesman said: “The Football League has been made aware that a number of arrests have been made in relation to an ongoing police investigation.
“We will provide our full co-operation to the relevant authorities. Given that it is an ongoing matter, we cannot comment further at this time.”