The Chhattisgarh government used a helicopter to transport the board examination question papers to an exam centre located in an interior pocket of Naxalite-hit Sukma district in the state, officials said on Friday.
The Maoist blast took place around 3 pm near Timmapuram village between Silger and Tekalgudem camps of security forces, over 400 km from the state capital Raipur.
The incident took place in the morning under Jagargunda police station area when a team of the CRPF's 165th battalion was out on an anti-Maoist operation, a police official said.
Women, children and other family members of the deceased were seen crying while women security personnel were trying to console them.
The explosive, however, remained "undetected" during the demining exercise conducted a day before the attack on Wednesday, they said.
A CAF constable was killed, while another was injured when a pressure bomb went off allegedly set by Maoists.
The personnel belonging to the CRPF's elite Commando Battalion for Resolute Action unit, the District Reserve Guard and the Special Task Force were involved in the operation.
A search operation was underway on Sunday to trace 18 security personnel who went missing after a fierce gun-battle with Naxals in a forest along the border of Bijapur-Sukma districts in Chhattisgarh, police said.
Roads are of great importance to win the war against the rebels in Sukma
At one location, seven bodies of the troops were recovered and the tree trunks bore bullet shots, indicating that a fierce gun battle took place in the area.
The Maoists rained bullets from light machine guns and used low-intensity improvised explosive devices to mount the attack that went on till evening.
The encounter, which took place in the jungles of Silger, a "liberated" Maoist zone between the naxal hotbed of Jagargunda and Basaguda in Dantewada, was launched on Thursday night by the CRPF from three directions.
CRPF Inspector General Pankaj Kumar Sinh said a joint team of CRPF jawans and state police deployed in Jagargunda area of Dantewada had gone for area domination exercise when about 200 Naxals started firing at them near Aasrampura village.
A contingent of 1,500 personnel drawn from six security camps launched the cordon and search operation against Naxals along Bijapur-Sukma border around the crack of dawn on Saturday.
Police sources said bodies of Jagargunda Station House Officer Hemant Singh and four others were recovered from the area
He said in most of the Naxal attacks, it has been noticed that villagers were used as human shields by the insurgents during the gun battle.
Ahead of Congress President Sonia Gandhi and BJP's Prime Ministerial candidate Narendra Modi's rallies in Chhattisgarh on Wednesday, security forces averted a possible landmine explosion, as they diffused two Improvised Explosive Devices weighing 50 kg in the Dantewada area of the state.
Three youths from Pune, who were allegedly abducted by Naxals while they were on a bicycle rally to spread the message of peace, have been released by the rebels in Chhattisgarh's Sukma district, police said.
The local intelligence wing had suggested not to carry out large anti-Naxal operations in south Bastar forests, where the ultras recently killed 14 Central Reserve Police Force personnel, citing geographical complications and strong Maoist 'Jantana Sarkar' network, a senior police official said.
Police have also recovered a GPS device of Naxals from the site in which the rebels had set the location of the improvised explosive device used in the incident.
From walking up to 10 kms to crossing rivers and spending nights in Naxal-hit areas, the poll officers will have to go past numerous hurdles and face life-threatening challenges to do their duty, but none of them is complaining.
The Maoists squad 'very discreetly with the aid of locals' kept tracking the movement of the troops when one party of 36, out of the total three, sat down for launch, the strong squad of Naxals, possessing sophisticated weapons, took them by surprise.
'It is an ambush, and no IEDs were used, which means it is more tactical, more technical and more intelligent.'
An injured jawan said around 10-12 Naxalites must have got killed in the 'befitting' retaliation by the CRPF contingent.