SP Atmaram Despande said the investigations so far showed IED was used in the blast and the two activists of Sanatan Sanstha who perished in the incident probably wanted to target the crowded Diwali-eve market.
He said charges of waging war against the state have been pressed against the deceased Melgunda Patil and Yogesh Naik, who were activists of the Sanstha, under the Unlawful Activities (Prevention) Act, 2008.
The blast had taken place at 9.30 last night when explosives kept in a scooter went off on a busy street in Margao, 30 km from here.
Home Minister Ravi Naik said the explosives may have got triggered before being planted at a designated spot.
"They wanted to disturb a traditional Diwali-eve event 'Narakasur' effigy competition in the heart of the town as the blast took place only a few metres away from the competition venue," he said.
Police raided Sanatan Sanstha headquarters at Ramnathi in Ponda town, 20 km from Margao, following the blast and four persons owing allegiance to the Sanstha were detained for questioning, SP Bosco George said.
Some Hindu right-wing groups came under scanner in Maharashtra after sadhvi Pragya, Lt Col S P Purohit and several other activists were arrested in connection with the Malegaon blast of September 2008.
Two of the detained persons have been identified as Suresh Naik, brother of Yogesh Naik, and Virendra Marathe, manager of the ashram where activities of the Sanstha are run.
Suresh Naik was the owner of the scooter in which the explosives were kept. He had bought the vehicle from the Sanstha's disciple Nishad Bakle four years ago," the SP said.
Meanwhile, the Sanstha denied the allegations against it terming them as "baseless".
"Based on searches conducted at the ashram in Ramnathi, the institution is being portrayed as an accused in Margao blast. Media should not jump the gun and should wait for proper judicial process to get over," it said in a statement.
"Sanatan will never encourage or support such activities in its ashram. The disciples have cooperated with the police during their search of the ashram on October 16 and will continue helping police in their job," it said.
Within half an hour of Friday's explosion, bomb disposal squad detected and defused another bomb with an electric circuit, a clock, four gelatin sticks and a detonator at Sancoale, 20 km from the blast site.
"We have recovered mobile and other gadgets from the place where both of the Sanstha activists were staying," Naik said, adding when the ashram was raided at Ramnathi last night, there were 250 people present in it, some from Maharashtra.
Terming the incident "very serious", he said he has asked police to investigate without any "political interference".
"There is every possibility of a political interference in the case. I have asked police to do their job as an independent authority," he said, refusing to elaborate on the issue of "political interference".
