Carnivore Keeper Rosa King with the tigers at Hamerton Zoo Park, on World Tiger DayCredit:Peterborough Tel / SWNS.com The district council, which is responsible for issuing the zoo’s licence, said: “Both the police and the council are working together within routine protocols to progress investigations into the incident as efficiently and effectively as possible.”It has emerged the zoo’s owners were warned about their ageing barriers four years ago.The zoo described Ms King’s death as a “freak accident”, but it was heavily criticised in an inspection by officials in 2013 that forced it to make improvements. A Cambridgeshire Police spokeswoman said the decision to collaborate on the case had been made on Tuesday afternoon, but could not say why the force had changed its mind.A spokesman for the zoo said it was “co-operating fully with the investigation that is currently being conducted by Huntingdonshire District Council Environmental Health Department”. The wildlife park opened in June 1990 and covers 25 acres. It includes enclosures for Malaysian tigers, Bengal tigers, cheetahs, wolves, corsac foxes, kangaroos as well as a variety of birds, reptiles and domestic animals.The zoo opened a new enclosure for its Malaysian tigers in July last year. Police have launched an investigation into the death of zookeeper Rosa King, who was mauled by a tiger, despite previously describing it as “non-suspicious”.The 33-year-old was fatally attacked during an incident at Hamerton Zoo Park near Huntingdon, Cambridgeshire, on Monday.Emergency services were called to the scene at around 11.15am but initially described Rosa’s death as “non-suspicious”. However, they have since launched a joint investigation with Huntingdon District Council, and officers were today seen arriving at the zoo. Show more Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.