The Mayor of Bristol said the new Banksy artwork belongs to the city council and removing it would be "stealing" as the row over the picture continues.
George Ferguson said he's "pretty sure" the removed Banksy "belongs to us" and "on the face of it would be theft".
A police officer and a PCSO were also seen at the boy's club, but a police spokesman said: "There have been no formal reports and there is no police investigation at the moment.
"We visited in an informal capacity following media and public interest. We offered advice on crime prevention and any issues which may arise from a possible sale."
The manager of the youth club who has laid claim to the latest Banksy artwork said yesterday he has received death threats after he "took an opportunity" to save his struggling youth service by removing the artwork.
Dennis Stinchcombe MBE, leader of struggling Broad Plain and Riverside Youth Project, said he had taken around 40 phone calls from angry street art fanatics.
He said: "People have been calling up and telling us we have no right to take it down, that it is public and we are stealing.
"People have even said they are going to come down here and sort us out, all sorts of nasty things to us. We have even had death threats."
He said if he hadn't taken the artwork "someone else would have and I wasn't going to let that happen".
Bristol City Council is yet to comment, and local police have not opened an investigation following the removal of the work.
CCTV has filmed a group of mystery men installing the latest Banksy art piece in Bristol in the early hours of Sunday morning.
After arriving in a white van, the group, dressed in high visibility jackets, brought out a blue canvas and walked around the side of the van.
The new Banksy street art has been dubbed 'Mobile Lovers' in Bristol and has already been taken away by the local Boys Club to prevent vandalism - and replaced by a replica.
A youth club leader has removed a Banksy mural hours after it was located to central Bristol. Mobile Lovers was posted to the street artist's website on Monday but its location was not disclosed.
Dennis Stinchcombe, the leader of the Broad Plain & Riverside Youth Project, whose property is where the Banksy was found, said: "I was approached by somebody who knows Banksy very well.
"We need £120,000 to keep going and our fundraising appeal has so far only brought a few thousand pounds. Now we've ended up with a Banksy on our doorstep. It is a dream come true. I'm absolutely buzzing.
"If anyone wants to see it they can come in here and put a donation in the box if they feel like it."
A Banksy artwork has been removed from the wall it was screwed to - just hours after it was tracked to a location in central Bristol.
Mobile Lovers was posted to the celebrated street artist's website on Monday but its whereabouts was not disclosed. It was later tracked down to Clement Street.
But at 4pm, a group of men from the financially struggling Broad Plain & Riverside Youth Project - situated just beside the piece - used crowbars to remove it.
A sign appeared on the boarded up doorway stating: "NOTICE: The new Banksy piece is being held by our club to prevent any vandalism being done. You are free to come and view but a small donation will be asked of you. Thanks."
Dennis Stinchcombe MBE, 58, leader of the youth project, said he had been urged to take the piece by a friend of Banksy.
A mystery piece by Banksy that appeared online yesterday has been found by ITV News.
The mural, which would be Banksy's first official work since his New York 'residency' last year, depicts a couple embracing while looking over each other's shoulders at their phones.
The piece is thought to be on Clement Street, just off the M32, and next to the entrance of Broad Plain Boys' Club in central Bristol.
Mysterious new mural in secret location is set to spark a nationwide search by the street artist's fans.Read the full story ›
A Banksy-esque mural showing shady surveillance agents eavesdropping on a telephone box has appeared on a street in Gloucestershire.Read the full story ›
Graffiti artist Banksy has re-worked his famous 'Balloon Girl' to mark the third anniversary of the Syria conflict.
On his website, Banksy writes of an incident in the Syrian town of Daraa on March 6, 2001, in which 15 children were arrested and tortured for painting "anti-authoritarian graffiti".
It goes on: "The protests that followed their detention led to an outbreak of violence across the country that would see a domestic uprising transform into a civil war displacing 9.3 million people from their homes."
On March 15, vigils will be held across the world to mark the anniversary of the crisis. They are being organised via #withsyria
'Kissing Coppers' was painstakingly removed from the wall of a pub and transported to the US in 2011.Read the full story ›