SEOUL, Jan 25 (Reuters Life!) - South Korean police are investigating a local cram school suspected of using paper cutters and electronic devices to copy questions from the leading U.S. college entrance SAT exam and passing them to students.

The probe, widened on Monday, is one of several in South Korea in the past few years where law enforcement officials in the education-obsessed country have gone after cram schools thought to have stolen standardised test material.

Police have questioned four people working for an expensive South Korean cram school that guarantees high scores for its students taking the SAT, widely known as the Scholastic Aptitude Test that can determine entry into a top-notch U.S. university.

"The four smuggled paper cutting blades in erasers into the test centre and worked together to systematically cut out questions from the test sheets," a police official said.

The group includes an instructor at the cram school and three college aged-students who were paid 100,000 won ($87) to cut out various exam questions and record others on calculators that are allowed into test centres, the official said.

The group, suspected of stealing test material for about five months, used the questions to help other students prepare for upcoming tests. They also sold questions to students in U.S. time zones who would take the same exam several hours later.

The group that administers the exam, ETS, in 2007 cancelled SAT scores from 900 test-takers in South Korea who were thought to have received stolen test material from a local cram school.

Parents in South Korea spend nearly $20 billion a year, or about two percent of the country's GDP, on private education and cram schools to help students prepare for college entrance exams at home and abroad, government data said.

There are about 100,000 South Korean students at U.S. universities.