HELSINKI (Reuters) -- Finnish police have arrested four more soccer players as part of an ongoing investigation into match-fixing, the force said on Thursday.

The four arrested on Wednesday are all from the Rovaniemen Palloseura club.

"It's hard to give out too much information as the investigation is ongoing," Detective Superintendent Jukka Lakkala told Reuters, confirming the arrests by telephone from Rovaniemi where the club is based.

The arrests bring to 11 the number of players being investigated in relation to allegations of match-fixing during the 2010 season. Six players remain in custody with a further five banned from leaving the country, Lakkala added.

HJK Helsinki midfielder Dominic Yobe, who was questioned by police last week, has been released from his contract, a statement on the club website (www.hjk.fi) said.

The club could not be reached for comment.

Detective Lakkala said it may take a while before charges are brought against any suspect in the case as police are still not sure of the extent of the match-fixing.

"It is not easy to say, as we don't know how large this case is at this point," he said.

The investigation began following the apprehension of a Singaporean man at Vantaa airport in Finland last month.

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