BEIJING - Chinese police have detained three people for running a high-tech cheating scam involving wireless microphones during the national college entrance exam, Xinhua news agency said Friday.

Parents wait as their children take the National College Entrance Exams in Shanghai, June 7, 2007. [Reuters]

A record 10 million Chinese high school students sat for the exam Thursday and Friday, competing for just 5.7 million university places.

It means make or break for the students and has spawned a string of cheating scandals in recent years.

Police in Jiutai, in the northeastern province of Jilin, became suspicious when a mini-bus remained parked outside a school hosting the exam Thursday, Xinhua said.

Inside, they found three people, "two of them staring at a computer screen and talking into a walkie-talkie," Xinhua said.

A student in the examination hall used a wireless microphone to read out the questions and received the answers from the van, Xinhua quoted their confessions as saying.

The three had charged the student 12,000 yuan ($1,500) for the service, it added.

Security for the exam is tight and exam papers are considered state secrets before the tests.

Authorities in neighboring Liaoning province spent 100 million yuan fitting over 8,000 exam halls with metal detectors and cameras to prevent tech-savvy students from cheating on national university entrance tests.

Police had found some 42 pairs of so-called "cheating shoes" with transmitting and reception ability, selling for about 2,000 yuan each, in a flat in Shenyang, the provincial capital, state media said Thursday, adding that they - along with "cheating wallets" and hats - had proved popular this year.

Three men in the southwestern province of Sichuan received suspended jail terms of 8-12 months last year for using pinhole cameras to send out images of the entrance exam papers to be worked out by "hired guns" for 19 students.