Prosecutors investigating the election bribery suspicions engulfing National Assembly Speaker Park Hee-tae have confirmed that Park's election camp cashed 50 million won ($44,830) worth of checks right before he was elected as the ruling party's chairman in 2008, a new piece of evidence which could support allegations that he bribed fellow lawmakers during the election.

Park is facing suspicion, raised by lawmaker Koh Seung-duk, that he distributed cash-stuffed envelopes to fellow ruling party lawmakers and district party council members to muster votes for his 2008 bid to become the head of the then Grand National Party, which recently changed its name to the Saenuri Party.

Park dropped his party affiliation to become the parliamentary speaker in 2010.

In the latest findings in their probe into the scandal, the prosecution found that Park's aide traded in 50 million won in checks for cash, which they suspect was then possibly used to grease the palms of party members before the July 3 election for the chairmanship, prosecution sources said.

The check cashing took place only about one week before the election, according to the sources.

As prosecutors scurry to track down where the 50 million won in cash was actually spent, they will summon Cho Jeong-man, Park's key finance aide who obtained the cash during the election time, on Thursday, the prosecution said. An arrest warrant will possibly be sought for Cho due to his previous inconsistent statements to prosecutors.

Prosecutors are reportedly also studying whether to call in Kim Hyo-jae, now the senior secretary for political affairs to President Lee Myung-bak, who is suspected of having played a key role in the bribery scheme while he was one of Park's close aides for the 2008 election.

Park's side, however, dismissed prosecutors' suspicion over the 50 million won in cash, saying the money was spent to cover Park's traveling expenses during the election and other costs for election campaign workers.