There was however no report of any casualty in the explosion, which took place on the National Highway-30 that connects the districts of Bastar zone in south Chhattisgarh with Raipur.
Four jawans were later air-lifted to Raipur for urgent medical treatment.
The ill-fated van was carrying the inmates to Jagdalpur jail after they were produced before the court at Kondagaon.
Additional forces have been rushed to the site and the search operation intensified in the area following the blast, the police said.
The Dankaranya Special Zonal Committee (CPI-Maoist) has given a call to observe a protest week in Bastar region from June 1 against the Green Hunt (anti-rebel chase) operation, training of Army in Bastar and demanded the withdrawal of paramilitary forces.