Some of South Korea’s biggest private education academies and star lecturers are under police investigation for allegedly purchasing state-administered college entrance exam, or Suneung, questions from teachers who participated in making them.

The list of those being investigated includes the so-called big three hagwon, or private education institution firms -- Megastudy, Sidae Injae and Daesung Hagwon -- as well as Hyun Woo-jin, a star math instructor at Megastudy, according to local reports and education insiders on Wednesday. The Education Ministry has requested the police to look into alleged irregularities in the operations of hagwon and possible collusion between public educators and the private education industry.

Apart from the three franchise tutoring services, six companies related to Daesung Academy -- including Gangnam Daesung Hagwon and Noryangjin Daesung Hagwon -- private academies for Suneung re-takers, a publisher, a research institute and a research center focusing on examining under the institution are also undergoing inspection. A textbook publishing company operated by Hyun is also among those targeted.

A private education firm called Etoos, along with a mock test and textbook company under Jongno Academy are also suspected of purchasing exam questions from Suneung test makers. Two star math lecturers and a geography instructor at Daesung MIMAC, an online education service website run by Daesung Hagwon, are also being probed.

On Wednesday, the Fair Trade Commission issued an audit report to nine private education companies, including Megastudy and Sidae Injae, for allegedly violating 19 laws in operating the hagwon. The market watchdog will also hold a deliberation to determine whether sanctions should be imposed and their scope should they be implemented.

The Ministry of Education declined to comment on the issue, as the case is currently under investigation by the police and the Board of Audit and Inspection.

The latest crackdown comes as part of the government’s efforts to reduce households’ hefty reliance on after-school cram schools by eliminating questions that require university-level knowledge. The ministry also aims to eradicate hagwon which force students and parents to pay for their own education materials and pressure them to enroll in score-boosting classes.

Last month, the ministry said it had caught 24 high school teachers for illegally selling exam questions to private education institutions before or after they took part in making questions for the Suneung and its mock exams. It has filed criminal complaints against four of the teachers on charges of obstruction of business, according to officials. Under the current law, Suneung test makers are obliged to keep all test-related information confidential. The ministry also requested an investigation into 22 of them on suspicion of breaching anti-graft laws.