The gruesome tale of India’s “house of horrors”, a serial murder case that has transfixed the nation for a week, took an intriguing twist yesterday when forensic scientists investigating the killing of at least 17 people in an upmarket Delhi suburb prepared to apply truth serum to the two prime suspects.

The decision came as further grim evidence emerged from the Noida bungalow where the bodies of women and children were discovered last month stuffed into rank-smelling storm drains. Thbodies were sliced up in such a clinical fashion that police have refused to rule out the possibility that they were killed for the human organ trade.

Moninder Singh Pandher, a businessman, and his servant Surender Koli were whisked away to a science laboratory in the state of Gujarat — about 620 miles away from the capital — where they were injected with sodium penthanol.

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Dinesh Yadav, the investigating officer, said the pair will also undergo lie detection and brain-mapping tests to monitor their reaction when they are shown photographs of the victims. The results of these tests cannot be admitted as evidence in court but, after a controversial investigation in which the police have been criticized for ignoring possible leads, officers are keen to find out as quickly as possible exactly how many victims there were.

“We will also examine their behavior and response to several questions,” J. Vyas, director of the state-run Directorate of Forensic Sciences, said. The operation is expected to take up to three days.

The move is being seen as an attempt by the authorities in Uttar Pradesh to placate an increasingly irate public who believe the police turned a blind eye to the suspected serial killings because Pandher was from an affluent background and the victims were from poor migrant families living in an adjacent slum.

Police say Kohli has confessed to killing 10 children and 5 women. So far 17 bodies have been discovered and there is a growing suspicion that more have been killed. Local residents fear that up to 40 missing children may have been murdered by the pair since 2004.

Angry mobs waving placards demanding that police “Hang the culprits” have gathered at Pandher’s home since the skulls and bones were found in the backyard a week ago. Yesterday more than 100 people, including grieving parents, hurled rocks at police guarding the complex, which has become a target of abuse for the local poor generally dissatisfied with their treatment by officialdom.

In response to the public outrage that some of the deaths could have been avoided, the Indian government this week appointed a four-strong committee to investigate the role of the police. The panel, including members of the Women and Children’s Ministry, will report back in two weeks. Six officers have been sacked and three suspended for neglect of duty.

The sense of disgust with public officials was increased yesterday by insensitive comments from Shivpal Yadav, the brother of Uttar Pradesh’s Chief Minister, Mulayam Singh. Visiting the scene of the crimes, he reportedly described the murders as a “small and routine incident”. His brother did not change his plans to pay his respects as the case threatened to turn into an embarrassment for his administration.

Meanwhile, the line of investigation has turned to the possibility that Pandher and Koli lured their victims into the house with the offer of sweets, with the intent to harvest their organs, such as kidneys, for commercial gain and police are investigating a link between the two men and a local doctor. Maya Sarkar, a woman who worked as a maid for Pandher for two years, has also been taken into custody.

The torsos of the victims — 11 of whom were young girls — have not been recovered, but the post mortem report released on Thursday concluded that the necks had been severed from the bodies with “butcher-like precision”.