A "monkey-proof" public litter bin that was allegedly converted into a monkey trap by contractors hired to catch them is being investigated by two government agencies.
An animal welfare worker spotted the National Parks Board (NParks) bin on Old Upper Thomson Road at a site near Upper Peirce Reservoir Park where she had not seen it before.
It has a lid which the animals may find difficult to open - but this had been propped open and tied to some fruit, while peanuts had been scattered nearby as bait.
An unofficially modified lock had been added to trap the monkey once the fruit was disturbed.
NParks told The Straits Times that it was alerted to the trap on Monday and that it had been set up without its knowledge.
"We take a very serious view of this matter and are investigating the incident," said its conservation director Wong Tuan Wah.
The bin is believed to have been converted by three monkey catchers hired by the Agri-Food and Veterinary Authority (AVA) - which is also investigating.
Ms Sabrina Jabbar, 23, who works for the Animal Concerns Research and Education Society, discovered the device and dismantled it before heading to the nearby Upper Peirce Reservoir Park to see if any more had been set up.
When she returned she found three men resetting the trap.
"They were unhappy that it had been dismantled," she said. "When I told them what they were doing was wrong, they showed me their AVA permits and said it is legal."
She alerted NParks but the agency said that by the time an officer arrived that night, the trap was no longer there.
Ms Jabbar said the trap may have posed a danger to visitors to the Upper Peirce Reservoir Park because a trapped monkey may cause others to crowd around the bin.
They might view passers-by as threats and attack them.
NParks said last October it had fined AVA-contracted monkey catcher Jack Pang after he illegally set up a monkey cage trap in an area where he was not meant to be operating.
This was just 10m from Bukit Timah Nature Reserve - where catching animals is illegal without permission.
Contractors are believed to be paid for each animal captured. The AVA has said it checks the condition of all animals taken to it upon arrival.
It has said its contractors have to comply with its requirements on capturing, handling and transporting the animals.
"The AVA also conducts surprise inspections on our contractors regularly to ensure compliance," a spokesman had said previously.