Kottayam: IG M R Ajit Kumar on Sunday cited severe head injuries the reason for the death of 40-year-old Siby, who died while being in police custody.
Talking to the media, the IG said the investigation into the death is progressing according to the guidelines of the National Human Rights Commission.
Hospital sources had also said Siby, a father of three children, died following severe head injuries.
Casting a shadow of alleged custodial torture over the Kerala Police, Siby, who was taken into custody eleven days ago, died Saturday at the Government Medical College here.
Siby's relatives alleged that he was subjected to brutal custodial torture due to which he suffered severe head injuries.
Police, however, have refuted the charges.
Siby was taken into custody in a case relating to a fight with a neighbour and brought to the Medical College hospital on June 30 by police with severe head injuries.
Doctors said an emergency surgery was performed on him in the view of his serious condition.
Later he was put on ventilator support.
Chairman of the Kerala Police Complaint Authority, Justice K Narayana Kurup, had visited Siby when he was undergoing treatment at the hospital.
Parents of Siby alleged that the day he was taken into custody, police forced him to lie down in the rain in the veranda of the police station at Marangattupilly.
District Police authorities have said the Marangattupilly Police failed to take Siby to hospital for medical check up immediately after he was taken into custody.
State Home Minister Ramesh Chennithala has ordered a crime branch probe into the death, after CPI-M-led LDF seized the opportunity to target the Congress-led UDF government over the issue.
Alleging that brutal torture by police in custody on the night of June 29 caused death of Siby, who belongs to the Scheduled Caste community, LDF has called for a dawn to dusk shutdown in Kottayam district on Monday.
CPI-M state secretary and former Home Minister Kodiyeri Balakrishnan has demanded a judicial probe into the incident.
Talking to reporters in Kochi, Chennithala said an "impartial investigation" would be carried out by Crime Branch wing of the Kerala Police into the incident.
The Home Minister also assured stringent punishment if police were found guilty.
Georgekutty, Sub Inspector of Marangattupilly police station, has been suspended for alleged lapses on his part after taking Siby into custody.