Hundreds of angry students took to the streets of the Indian capital on Friday as police quizzed dozens of people over the leaking of high school exams that will force more than one million students to retake tests.
Police have questioned 45 people, including students and tutors, over the leak but no arrests have been announced.
Mathematics and economics exam papers were distributed on the WhatsApp messaging app prior to the tests, forcing the cancellations and sparking fury among students and their parents.
On a second day of protests, hundreds of students in New Delhi chanted against the exam board, which they accused of negligence.
Education secretary Anil Swarup said more than one million students will have to resit the economics exam on April 25.
The mathematics test may be held in July. This could be restricted to Delhi and neighbouring Haryana state, however, as an investigation found the leak was limited to these areas.
Around 1.6 million students nationwide had feared they would have to retake the maths exam.
"It is most unfortunate... that children have been made to suffer on account of someone else playing dirty tricks," Swarup said.
Cheating and exam fraud -- such as paying bribes to buy test papers -- is common in India. More elaborate ruses have included relatives scaling the walls of exam centres to give crib sheets to students.
The Central Board of Secondary Education exams are crucial for students hoping to attend India's most prestigious universities.
Angry parents and students have demanded answers from Prime Minister Narendra Modi's government, which has faced criticism over digital security in recent weeks, especially over an identity card database that holds the biometric and personal details of more than one billion Indians.
India's ruling and opposition parties have also accused each other of mining and sharing the personal information of people who follow their social media accounts or use their apps, similar to the recent Facebook data scandal.
That row erupted after a security expert alleged that user data of people linked to Prime Minister Modi's personal app was shared without their consent.