Two persons were arrested on Sunday in connection with the murder of Sekhar Ray, a businessman, in Shibpur, on November 23. Two other accused were arrested on Saturday.

Police claimed the investigation was nearing its end and that they would soon arrest the murder mastermind.

Roy was shot dead by a gang of five on the Howrah-Andul Road, leading to Vidyasagar Setu, in Mandirtala.

Accompanied by one of his employees, Roy was on his way to a bank in Burrabazar to deposit Rs 4 lakh. Narayan Khatua, the employee, was seriously injured in the incident.

Police had initially suspected that business rivalry was behind the murder.

After interrogating the four accused, the sleuths have identified the kingpin as Santosh, said Mihir Bhattacharya, superintendent of Howrah police.

Santosh is a resident of Howrah, but has links with criminal gangs of almost every town in West Bengal and Bihar.

?He had prepared the master plan for the murder and directed his men to keep a close watch on Roy almost round-the-clock for several days,? said a senior officer connected with the probe.

Police superintendent Bhattacharya told Metro that his men have obtained vital leads about the whereabouts of Santosh.

The two arrested on Sunday have been identified as Shankar and Baburam Mahato. While Mahato was picked up from Dhanbad, Shankar was netted from a hideout in Howrah.

?Both of them were involved in the murder and were present on Vidyasagar Setu when Roy was killed,? said Bhattacharya.

Howrah police are conducting regular raids on various parts of the city and have picked up a few suspects, mainly from central Calcutta, for interrogation.

Some suspects have been picked up from North 24-Parganas, too.

?Several persons are being questioned and a lot of leads are being explored,? said an officer working on the case.

Immediately after the murder, police had launched a series of raids in Bali, where a key suspect, named Kalu, was arrested.

?We interrogated him for days and he revealed details of the gang that had murdered the businessman,? said a senior officer.

On the arrest of the other two accused, the officer said Birbal Jaiswal had been picked up from Dhanbad and Satyam from a hideout in Shibpur. Cash, totalling around Rs 90,000, was seized from both.

Preliminary investigation revealed that Birbal, a resident of Liluah, had pulled the trigger, killing Roy on the spot. Police claimed that he has admitted to the crime.

Superintendent Bhattacharya said the gang had tried to rob the businessman at least four times.