A vet who performed postmortems on mutilated cats said a human is responsible for the gruesome deaths.
The cats that were found decapitated or with missing limbs were killed and then dismembered using a knife-like instrument.
The vet, who wishes to remain anonymous, told the BBC the pets were strangled and then taken off-site to be butchered, then the bodies returned, which is why no trace of blood has been found at the scene.
The ten cases of cats found in and around Croydon are being investigated by the Metropolitan police, but the actual number of deaths is believed to be as high as 50.
The RSPCA has been criticised by campaigners for failing to act after reports of mutilated cats were coming in as far back as October.
Collect picture of Amber the cat who belonged to Wayne Bryant that was found in a wooded area opposite their Croydon after being killed.See SWNS story SWCAT; A machete-wielding serial killer is on the loose and has been mutilating cats and keeping body parts as TROPHIES, an animal rescue shelter is warning. South Norwood Animal Rescue and Liberty (SNARL) is warning that a twisted killer is roaming Croydon, south London, and has slain dozens of cats in the last two years. The latest of killing was revealed on Saturday when a beloved pet was found on with gruesome wounds that appear to be the attacker's ìsignatureî. Boudicca Rising, who runs the shelter with partner Tony Jenkins, says a pattern has formed of cats being decapitated and having their intestines ripped out and displayed near their ownersí homes.
Amber the cat was found in a wooded area opposite her Croydon home (Picture: SWNS.com)
The South Norwood Animal Rescue and Liberty (SNARL) centre was forced to crowdfund for financial aid after being overwhelmed with reports of dead animals.
Boudicca Rising and Tony Jenkins, who run the centre, claimed the national branch of the RSPCA was still refusing to take their concerns seriously.
Rising told BuzzFeed News that the RSPCA has continuously denied it.
We did meet with them once, but they never got back to us.
It’s not that he [the RSPCA contact] was unhelpful, more than he was just bound up in all this bureaucracy. It is that bureaucracy that has screwed us.
There was a lot of frustration around the way people were being treated because these things had happened and they were not being believed.

Collect pictures of cat Ykiyo (Ukiyo) who was found dead. See SWNS story SWCAT; A machete-wielding serial killer is on the loose and has been mutilating cats and keeping body parts as TROPHIES, an animal rescue shelter is warning. South Norwood Animal Rescue and Liberty (SNARL) is warning that a twisted killer is roaming Croydon, south London, and has slain dozens of cats in the last two years. The latest of killing was revealed on Saturday when a beloved pet was found on with gruesome wounds that appear to be the attacker's ìsignatureî. Boudicca Rising, who runs the shelter with partner Tony Jenkins, says a pattern has formed of cats being decapitated and having their intestines ripped out and displayed near their ownersí homes.
Ykiyo was also found dead (Picture: SWNS.com)
An RSPCA spokesman told BuzzFeed News the charity is investigating the reports and are awaiting results on the cause of deaths.
There is a dedicated team working closely with the police and looking into all evidence given to us to see if there is deliberate cruelty involved.