Nineteen people have been arrested for the massacre last week of 16 people, including five children, in Bihar's Khagaria district, police said on Thursday.
While 12 people had been arrested earlier, seven more were nabbed between Wednesday and Thursday morning. Among those arrested and being interrogated for the Oct 2 killings in Khagaria's Amausi village, about 200 km from Patna, is the alleged mastermind OP Mahto.
"More arrests will be made soon," said Additional Director General of Police (headquarters) Neelmani.
"Combing operations in Khagaria and neighbouring districts are underway by a joint team of security forces, including Bihar Military Police, Special Task Force and Special Auxiliary Police," Neelmani added.
About 50 people are said to have taken part in the slaughter, including nearly two dozen people from Amausi village.
"Thirty-seven people were named in the FIR (first information report) and there were 25 unidentified people as well," said a police official.
Police have got some information from Paro Singh, the lone survivor and witness who managed to save his life by pretending to be dead after sustaining gunshot injuries.
The brutal killings, in which the hands of the victims were tied before they were gunned down, appeared to be over a land dispute, officials said.
All the victims belonged to the Kurmi caste and were from Amba Ichwara village, a few kilometres from the incident site. The attackers are believed to be from the Sada (Mushahar), a Mahadalit caste in Bihar considered the poorest of the poor, who are usually landless.
Though the massacre has been blamed on the outlawed Communist Party of India-Maoist, the group has denied involvement and claimed it "has nothing to do with the incident".
Khagaria District Magistrate Abhay Singh admitted that the incident had led to tension in the area but matters were under control.
A large number of security personnel have been deployed in the village and neighbouring areas to prevent any retaliatory attack by members of the Kurmi community, the caste to which Chief Minister Nitish Kumar belongs.