DAEGU (Yonhap News) -- Prosecutors in Daegu said Friday they are questioning a key suspect in a widening investigation into match fixing in baseball.

Prosecutors in this southeastern metropolitan city, 300 kilometers from Seoul, said they were investigating a former college baseball player surnamed Kim. The 26-year-old allegedly introduced two active players in the Korea Baseball Organization (KBO), the nation's top baseball league, to a gambling broker to assist in match fixing.

Prosecutors said one of the two players, a member of the LG Twins also surnamed Kim, graduated from the same high school as the ex-college player. Prosecutors have not yet confirmed whether any bribe was offered for the introduction.

The broker in question, surnamed Kang, is under arrest for his alleged role in volleyball match fixing. He has testified that he was also involved in rigging baseball matches. Prosecutors have so far failed to obtain more concrete evidence beyond Kang's testimony, however. The KBO players Kang said participated in the fixing have both denied their involvement.

Prosecutors believe their questioning of the former college player will provide a breakthrough in their investigation into Kang's claims. Sources said prosecutors will also try to find out if Kim tried to involve more of his former high school or college teammates in fixing attempts.

Allegations of match fixing in volleyball's V-League surfaced earlier this month, with several current and retired players coming under investigation. The focus recently shifted to baseball, the nation's most popular professional sport, following Kang's testimony.

The government recently announced it will take a "zero-tolerance" approach against match fixing and toughened penalties for offending parties.

Last year, the K-League, the first-division football league, was rocked by a match-fixing controversy. Dozens of active and former players were indicted or found guilty.