KOLKATA: One person was killed in police firing and at least eight prisoners, jail staffers and policemen were injured after inmates of Dum Dum Central Correctional Home rioted on Saturday. Undertrial prisoners set fire to prison property and engaged security personnel in several rounds of pitched battles using bricks and axes and other sharp-edged weapons, forcing cops to open fire.Several prisoners tried to scale the 20-foot-plus walls of West Bengal ’s largest prison facility during the riot, which continued for over eight hours in the middle of a crowded Dum Dum neighbourhood; three others were caught trying to sneak out of the prison gates, officials said.The arsenal used by the prisoners indicated it was a “planned” jailbreak attempt, officials said, but there were three immediate sparks, all linked to Covid-19 fears and several steps implemented by the government over the last one week to control its spread.One of the immediate causes was a decision by prison authorities on Friday to suspend till March 31 the bi-weekly prisoner “interviews” with family members; this would have significantly reduced the number of jail visitors. Another trigger was a government proposal for a 15-day special parole for lifers who had already spent 10 years in prison with certified “good conduct”; this would have led to the release of 500 lifers and freed up several cells for use as isolation wards.The third issue that Saturday’s rioters mentioned was delayed court production of undertrials (courts are taking up only urgent matters and encouraging more video-conferencing).The first inkling of trouble came around 10.30am on Saturday when a section of undertrials, demanding hand sanitisers and masks, “started getting agitated”, officials said. This soon led to the demand that they be allowed their weekend “interviews” with family members. This was followed by slogans against parole applications being turned down (even as lifers’ applications “were being allowed”).