Police from New Delhi raided several places on Monday in the state summer capital, Srinagar, in connection with the 29 October blasts in New Delhi that killed 62 people, said local police, speaking on condition of anonymity.
They said a man identified as Muhammad Hanief was arrested in the city's congested old district of Kawadara, and two or three other people were picked up elsewhere for questioning.
The latest raids follow the capture of alleged mastermind Tariq Dar, a suspected member of Pakistan-based separatist group Lashkar-e-Taiba, in Srinagar on Thursday.
Dar, who has not been charged, was linked to the blasts at two crowded markets and a bus through phone taps and bank records, newspaper reports in New Delhi and police said.
The arrest of Dar, an international drug company executive and father, who had broken links to a separatist group as a teenager surprised family members and a journalist who interviewed him for a book on Kashmir.
"When I last met him in December 2002, he had just got engaged to be married. He was, like anybody his age, excited about his first love," recalled journalist Pradeep Thakur in the Times of India.
Dar also used occasionally to write for Kashmiri magazine Mount Valley.
Now in his 30s, Dar apparently started out selling creams, bandages and baby oil from town to town until he was promoted and given sales responsibility for the entire Kashmir Valley.
He was in New Delhi on 5 October to receive a sales excellence award from his company, his wife said.
But police say he was also planning the deadly blasts that wounded 210 people ahead of the major Hindu festival of Diwali and the Muslim festival of Eid al-Fitr.
On Sunday, police said they noted Dar as a suspect after finding a debit card bill for a hotel stay in the first week of October.
They followed up by reviewing his bank account details, which showed that a wire transfer of almost $11,500 had been made by a person based in the Middle East days before the blast, police said.
Police said a subsequent tapped mobile phone conversation to Pakistan, during which Dar spoke about the blasts, confirmed their suspicions.
"We've got the transcript of the conversation. After that there wasn't any doubt left in our mind," an unnamed investigating officer told the Hindustan Times daily.