Police have detained 18 people suspected of selling high-tech cheating devices to students who sat the national college entrance exam, which ended on Wednesday.

Seven students were found to have used high-tech devices to cheat in the exam in Gansu province, local authorities said.

The exam papers of the students were marked zero and police detained three people who allegedly sold the devices to the students, said a spokesman with the education bureau of Jingyuan county in Gansu.

The supervisors found wireless earphones as well as ruler and wristwatch-like receiving devices on the students, who were caught in three examination halls in Jingyuan county on Monday and Tuesday, said the spokesman.

In a separate case in Central China's Hubei province, police on Friday detained four people who sold wireless communication facilities to help students cheat on the exam.

The police confiscated 11 sets of devices worth more than 100,000 yuan (US$14,640), according to the public security bureau of Honghu city.

The suspects allegedly charged a 2,000-yuan deposit for each device. After the examination, the buyers were to pay another 5,000 yuan, it said.

Meanwhile in Southwest China's Guizhou province, 11 people have been detained for involvement in a cheating scheme, according to the local government.