The family of missing Siwan businessman Hari Shankar Singh, suspected to have been kidnapped from the district's Pachrukhi station on Sunday morning, is yet to receive any ransom call.

Inspector-general (Tirhut zone) Paras Nath said on Monday four suspects have been picked up for interrogation in the case, but no substantial clue about the whereabouts of the victim or his alleged abductors has been found.

"The victim's family has been persuaded to cooperate with the investigating team," Nath said.

On Sunday, Hari Shankar's family was upset that the cops didn't launch the search operation fast enough, and residents had blocked rail and road traffic in protest over the incident. A police officer was also suspended.

Siwan superintendent of police Saurabh Kumar Sah said the kidnappers have not yet made any ransom call. "We are keeping a close watch on the activities of criminals operating in Siwan and adjoining districts," he said.

The special investigation team probing the case - headed by additional superintendent of police Arvind Gupta - carried out raids at suspected hideouts of a gang led by Ayub and Rayeesh Khan of Siwan, but there is nothing to link the gang to the case.

An investigating officer said that a relative of a gang leader had unsuccessfully contested the Assembly election from Raghunathpur in Siwan.

The victim's family denied reports that the Khan brothers (Ayub and Rayeesh) had demanded money from Hari Shankar before the polls.

Police sources said raids were also conducted in Siwan town to check if associates of former RJD MP Mohammad Shahabuddin, who is serving a life term in Bhagalpur central jail for kidnapping, were involved in the abduction.

On Monday, Pachrukhi's traders downed shutters to protest rising crime in the area.