They said Negi was arrested from the state and has been sent to their custody till November 20. The SP is the ninth person to be arrested in this case by the Central Bureau of Investigation.
The CBI is also expected to file a charge sheet in the case soon. The central probe agency had in August arrested eight Himachal Pradesh Police officials, including Inspector General Z H Zaidi, in connection with the custodial death of Suraj Singh, a 29-year-old labourer from Nepal.
Singh, who was a suspect in the rape and murder of a minor school girl in Kotkhai area of Shimla in early July, was among six people arrested by the local police.
He was allegedly killed by a co-accused at the Kotkhai police station last month, triggering a massive public outrage.
The CBI, which was later handed over the probe into the case by the Himachal Pradesh High Court, questioned several people before arresting Zaidi, a 1994-batch IPS officer, the then IGP (South) Manoj Joshi, the then Deputy Superintendent of Police, and six other police officials.
The Himachal Pradesh Police had arrested Ashish Chauhan alias Ashu (29), a resident of Sharaal village in Mahasu area of Kotkhai; Rajender Singh alias Raju (32), a driver; Subash Singh Bisht (42) and Deepak alias Deepu (29), both residents of Pauri Garwal; Suraj Singh (29) and Lok Jung alias Chotu (19), both hailing from Nepal.
A 16-year-old girl had gone missing after school hours on July 4 from Haliala forest in the Kotkhai area of Shimla district. Her naked body was found in the forest on July 6 and the post-mortem report confirmed rape. The rape case has created furore in the state which goes to polls later this year.
The case was handed over to the CBI by the Himachal Pradesh High Court on July 19 on the state government's plea amid public outburst against the state police.
The CBI had filed two FIRs on July 22.