Lord Stevens' inquiry into football corruption has been extended by two months to investigate 39 transfers.
Lord Stevens will spend a further two months investigating corruption
The former commissioner of the Metropolitan Police examined 362 transfers which took place between 1 January 2004 and 31 January 2006.
The 39 transfers involved eight clubs and need "further investigation" before Lord Stevens will "sign them off".
After reporting his findings to the Premier League, he added: "This interim report remains a work in progress."
A total of 29 clubs have been members of the Premier League during the period covered by Lord Stevens' inquiry.
Richard Scudamore, chief executive of the Premier League, said Watford, Sheffield United and Reading - who were promoted to the Premiership in the summer - were not part of the investigation.
And Scudamore said Leeds were not involved as they did not buy or sell any players as a Premiership club during the period under scrutiny.
WHAT IS A BUNG?
A secret and unauthorised payment seen as a financial incentive to help a transfer go through
HOW DOES IT WORK?
An agent pays a club official a slice of his cut for the help of the club official helping the transfer go through
An agent may... never so approach a player who is under contract with a club with the aim of persuading him to terminate his contract prematurely or to flout the rights and duties stipulated in the contract
"Those four clubs are no longer party to the inquiry, but the 25 clubs which remain are," Scudamore said.
"Those 25 clubs wished to express solidarity with their colleagues, and there was no call for the eight clubs to be identified and therefore - mathematically what would be the remaining 17 clubs - to be released from the inquiry."
The identities of the clubs involved and the transfers are being kept secret but if they are deemed to have involved illegal payments then Lord Stevens will pass details to the Premier League, the Football Association and, if necessary, the police.
The eight clubs who are still part of the inquiry have not yet been informed.
Lord Stevens has declared 323 transfers as being clean and he will now seek to use Football Association rules to force agents to open their bank accounts as investigations continue into the remaining 39 transfers, most of which are domestic transfers.
The FA confirmed that it has the right to request information from FA-licensed agents' bank accounts under their "powers of inquiry" - and those who failed to comply risked a misconduct charge.
An FA spokesman said: "If we are asked to try to obtain information from agents under our powers of inquiry we will of course do so."
Lord Stevens said he was confident that the inquiry would "get to the bottom of what the problems are."
"This is not an easy inquiry but we will do everything in our powers to make sure it is a successful one," he said.
Scudamore added: "If there is any criminal activity we will pass that to the police."
The Stevens inquiry was set up by Scudamore after allegations of corruption were made earlier in 2006.
The most notable of those came from Luton manager Mike Newell, who said he had been offered bungs.
Scudamore denied that he asked Lord Stevens to launch an inquiry because of Newell's comments, or those made at the same time by former England boss Sven-Goran Eriksson, who claimed three unnamed Premiership clubs were riddled with corruption.
The Premier League says the report was commissioned simply to find out where money in football transfers went - to clubs, players or agents - and if there were illicit payments to managers.
But Lord Stevens, who served with the Police for 43 years before retiring in January 2005, only has the power to make recommendations.
The issue of illicit payments in football returned to the spotlight in September after an undercover BBC Panorama investigation into bungs.
That was followed by Blackpool chairman Karl Oyston and England manager Steve McClaren's agent Colin Gordon making claims about bungs in football.
The Football Association has already responded to the expected findings by strengthening its compliance department that looks into the behaviour of agents and suspect transfers.
But some within football would like the regulations to go further - including a new rule determining that players pay agents a set percentage of their income, as happens in showbusiness, instead of the agents negotiating their own one-off payments.
WHAT THEY SAY:
It has needed to all come out in the open - and that is not a problem. Whatever happens, we'll wait and see but for me it is not a problem.
Portsmouth manager Harry Redknapp
The game is not awash with corruption but there are dark corners and we'd like some light shed on them. If you're one of the agents who's done wrong I'd get concerned because I think this guy means business.
Jon Smith, football agent
What surprises me is that there are that many clubs involved - all the managers I've dealt with are very straight and moral. I personally have never had anyone say anything untoward to me - eight clubs is a large proportion of the Premiership, but there's further investigation so let's not get carried away.
Sky Andrew, football agent
It will be the start of the clean-up of the game. From now onwards, the whole transfer system will end up being completely overhauled and will be monitored in a lot closer way.
Former Football Association compliance officer Graham Bean, football agent
It is not a surprise that definitive evidence is very hard to find. You are talking 'Magic Roundabout' money with all the different agents involved - and you need to do a proper forensic trail, otherwise the trail can stop dead.
Professional Footballers' Association chief executive Gordon Taylor