8.75 lakh candidates were appearing for the exam in Gujarat.
Four people, including two Bharatiya Janata Party (BJP) workers and a sub-inspector, were arrested on Monday in connection with the police constable recruitment exam paper leak, an official said.
The exam was cancelled hours before it was scheduled to commence on Sunday after authorities learnt that the paper had got leaked.
As many as 8.75 lakh candidates were scheduled to appear for the exam at 2,440 centres across Gujarat.
Since two of the accused - Manhar Patel and Mukesh Chaudhary - were associated with the ruling BJP, the state party unit ordered their suspension with immediate effect following their arrest.
The other two accused are Rupal Sharma, who worked at a hostel in Gandhinagar and is the daughter of a former police sub-inspector, and sub-inspector VP Patel, posted at the wireless department in Gandhinagar.
Chaudhary and Sharma were also supposed to appear in the examination, a senior police official said.
He said the main accused, Yashpal Solanki, was still at large and efforts were on to nab him.
The paper was leaked from Delhi by Solanki, a native of Lunawada in Mahisagar district. He worked as an ad-hoc employee of the Vadodara Municipal Corporation, he said.
Solanki allegedly went to Delhi on the night of November 30 and managed to get answers of some of the questions to be asked in the written exam, the officer added.
"He flew back to Vadodara the next day and passed on answers of the questions to be asked in the paper to some people, including Manhar Patel, who in-turn passed them to Chaudhary," he said.
Manhar Patel was a BJP worker from Bayad taluka in Arvalli district while Chaudhary was an elected member of Vadgam taluka panchayat of Banaskantha.
"As per their plan, Manhar Patel, Chaudhary, Sharma and eight to ten other candidates gathered at Sharma's hostel on Sunday morning to discuss the leaked questions. After going through the answers, they all dispersed," he said.
He said sub-inspector VP Patel, who knew Manhar Patel, also wanted the answers for some candidates who were appearing for the exam.
The sub-inspector has been suspended following his arrest, he added.
Preliminary investigation has revealed that no money was paid to anyone for leaking the question paper, however, things will be clear after Solanki's arrest, Chavda said.
"We have formed teams to nab him. Some other accused are also on our radar," he said.
After the names of the two BJP workers cropped up in connection with the offence, the state party unit chief Jitu Vaghani issued a statement saying that both of them have been suspended from the party.