By Subir Bhaumik
BBC News, Calcutta
The blasts took place in busy areas
A policeman has been arrested in connection with the last month's bomb blasts in India's north-eastern Assam state which killed more than 80 people.
Constable Chandra Bodo was arrested on Monday for allegedly planting a bomb in a car in the state's capital, Guwahati.
Bodo had links with some separatist rebels blamed for the explosions, the police said.
Police suspect the separatist United Liberation Front of Assam (Ulfa) is behind the blasts. It denies any role.
Police said that constable Bodo allegedly planted a bomb in a car and parked it in front of a court in Guwahati.
Nearly 30 people were killed in that explosion alone.
The Indian home ministry says it also has evidence of the separatists' involvement in the October 30 bombings.
It fears more such blasts after some separatists were arrested with powerful explosives in the last two days.
"We have information from federal intelligence agencies suggesting that the separatists carried out these heinous attacks," a senior interior ministry official told the BBC.
"We suspect they could have links to Islamic radicals based in Bangladesh but we need more specific information on that," he said.
Bangladesh has denied any role in the explosions.
In a statement, its foreign ministry asked India to stop "finger pointing without appropriate evidence".
The statement came after a spate of media reports quoted senior Indian officials who blamed the explosions on "Bangladeshi-based jihadis".
The Assam police has detained several people who provided cars and other logistics for the explosions.
The police said they had all been found to have close links to the Ulfa and the Bodo group, National Democratic Front of Bodoland (Ndfb).
The Ulfa is the leading Assamese separatist group, the Ndfb fights for an independent homeland for the Bodo tribe.
Both groups have denied any involvement in the explosions.
Ndfb is involved in negotiations with the Indian government with a ceasefire in place.
But both the groups have a history of involvement in serial explosions.
In the last seven years, dozens have been killed in these explosions.