SEOUL, South Korea — The South Korean police said Monday that they were pressing criminal charges against 21 people, including two professional baseball pitchers in the KBO League, on suspicion of match fixing.

In 2014, the pitchers, Lee Sung-min of the NC Dinos and Yoo Chang-sik of the Hanwha Eagles, deliberately walked batters in return for gifts and cash from match-fixing brokers, the police said. Lee now plays for the Lotte Giants and Yoo for the Kia Tigers.

The police said two NC Dinos officials covered up the match fixing when Lee confessed to it and then traded Lee to the KT Wiz for $875,000.

South Korea, the host for the 2018 Winter Olympics, has been rocked by several match-fixing scandals in recent years, with prosecutors hauling in professional soccer, baseball and volleyball players on suspicions that they had manipulated game outcomes in return for bribes from middlemen. Some of these middlemen were retired colleagues of the players and were working for criminal organizations, the authorities said.