NEW DELHI (AFP) - Three officials were arrested Monday for leaking a chemistry exam paper to students, which forced the test to be cancelled for the second time for the same reason.

Education authorities in southern Karnataka state last week cancelled the exam just hours before it was due to start after a student tipped them off about the leak.

The cancellation lead to violent protests by the class 12 students, who were initially meant to sit the test on March 21 but a leak of that paper caused the exam to be delayed.

"We have arrested three persons over the leaking of question papers. We are probing the role of many more," Sonia Narang, head of the criminal investigation department said.

One of the arrested officials is a personal assistant to the medical education minister in the state government, she said.

An estimated 174,000 candidates were due to sit the pre-university course test across the state.

Media reports said 40 education department employees had been suspended following the scandal.

The leaked paper was sold for as little as 1,000 rupees ($15) on the Whatsapp messaging service, police said.

The agitated students attacked the office of the examining body over the weekend in Bangalore city, which has said the test will now take place on April 12.

Cheating in exams is common in India, including the paying large bribes to buy test papers.

Last year hundreds of parents and relatives were arrested in eastern Bihar state for scaling the walls of schools and providing crib sheets and study material to students during exams.

Last month authorities in western state of Gujarat blocked mobile phone Internet services in many districts to stop candidates from cheating during a public sector jobs test.