On weekends, nature lovers and joggers are often seen in this part of the Rail Corridor near Sungei Kadut Avenue.
Its ties to Singapore's past lives on as it used to be the route along which train travellers journeyed to and from Malaysia.
But when night falls, the 300m stretch of Rail Corridor is frequented by another type of lovers - those in search of fast love and illegal nicotine kicks.
A two-day investigation by The New Paper revealed that the vicinity of the nature trail is being used by an outdoor prostitution ring and contraband cigarette peddlers.
We were first told about the activities by a jogger who declined to be named.
On two occasions in the past month, the 48-year-old man, who regularly runs along the Rail Corridor from Stagmont Ring to Sungei Kadut Avenue, was startled by what he saw at night.
He said: "It's very dark. As I got closer, I heard voices. I was surprised when I could make out the shapes of six to eight women sitting on plastic chairs surrounded by men."
The area is not popular with joggers because of slippery mud pools dotting the trail. But that has not stopped dozens of foreign workers heading into the Rail Corridor at night.
TNP staked out the area on Wednesday and Thursday. Between 9pm and 10.30pm, we witnessed a steady stream of men going into the state-owned land.
One of them, who gave his name only as Salim, initially told TNP that he used the trail as a shortcut to Yew Tee MRT station.
When pressed further, the Bangladeshi in his late 20s said with a smile: "Inside, there are also Ah Muis (Hokkien for girls), so I take a look while on my way. But I never try them - there are many mosquitoes."
Some workers claimed that a makeshift brothel has been in business in the area for the last five months, moving locations frequently within the Rail Corridor.
From our observation point about 50m across a muddy canal, we could see men looking at four women seated on plastic chairs.
Three men appeared to be pimps, acting as a liaison between the potential clients dressed in shorts, T-shirts and sarongs, and the women who were in tight tops, short skirts and hot pants.
Occasionally, one of the pimps would leave and patrol the area on a bicycle.
ILLEGAL ACTIVITIES NOT NEW TO AREA
The vicinity of Kranji and Sungei Kadut is no stranger to illegal nocturnal activities.
More than six years ago, the forest surrounding nearby Yew Tee Industrial Estate was a favourite haunt of contraband cigarette peddlers and buyers. Singapore Customs mounted many raids there and the peddlers would usually run into the dense vegetation when they were chased.
Across the road from Sungei Kadut Avenue, the former Kwong Hou Sua cemetery, which faces Mandai Estate, was once used as an outdoor brothel.
In a June 2009 report in The New Paper, a Mandai Estate security supervisor had said there were many places there to play hide-and-seek with the authorities.
He also said outdoor brothels were inevitable whenever there were dormitories or large congregations of foreign workers as the brothels catered to these workers.
During a visit to the area, TNP had found makeshift shelters and evidence of human activities there.
Some of the clients were then seen leaving with the women to narrow paths in the 2m-tall lalang vegetation. Light from torchlights or mobile phones were used to guide the clients and the women through the thick growth.
After about half an hour, the women would emerge with the clients and return to the chairs they had occupied earlier. The clients would then leave.
On the two days we were there, the women and the pimps left the area at about midnight.
We inspected the same area during the day.
Patches of lalang - the size of a small HDB bedroom - had been cleared to make way for "rooms". The cleared area was strewn with condom wrappers, candle boxes, soiled tissue paper and discarded packets of food.
Around the cleared area, there were wooden poles anchored to the ground. It is believed that plastic or canvas sheets are tied to the poles to create the "rooms".
But the outdoor brothel was not the only vice going on in the area.
TNP also witnessed the illicit sale of contraband cigarettes on both nights.
Closer to a locked gate facing Sungei Kadut Avenue, we saw three men take a stash of cigarettes from among the lalang.
From a big cardboard box, which can hold about 10 cartons of cigarettes, they separated the packs of cigarettes into loose boxes to be sold.
Some men bought the cigarettes before heading to the spot where the women were sitting.
Said the jogger who tipped off TNP: "This isn't Geylang, so it's amazing that this outdoor brothel is happening less than 200m from the closest HDB block in Choa Chu Kang."
RAIL CORRIDOR UNPOPULAR WITH NIGHT JOGGERS
Most joggers at the Pang Su Park Connector in Choa Chu Kang are unaware that the Rail Corridor, just opposite the park connector, is being used as a brothel.
Unlike the well-lit park connector, the Rail Corridor is "unknown territory".
Ms Tina Wong, 20, said: "Why would anybody want to jog where it's dark and unsafe? There's no telling what can happen there."
The Choa Chu Kang resident is among many who jog at night because it's cooler and less humid. School office administrator Douglas Lee said he had noticed shadows on the opposite bank of the jogging path.
The 26-year-old said: "I saw glimpses of people walking and strange lights, maybe people using their mobile phones to light the path.
"I jog at the park connector because I would be more aware of my surroundings at night."
Mr Lee has jogged in the afternoons along the 2km stretch of the Rail Corridor from Stagmont Ring to Sungei Kadut Avenue as it is more rugged and natural.
He said: "It's wonderful to hear the sound of insects or spot that lone monitor lizard as you jog."
The 26km-long Rail Corridor was formerly managed by Malaysia's Keretapi Tanah Melayu before it was handed over to the Singapore authorities in 2011.
Volunteers from the Nature Society (Singapore) patrol the corridor in collaboration with Singapore Land Authority, said Mr Paul Wonnacott, a coordinator for the Rail Corridor Watch Group. To date, they have not seen any illegal activities there.
Mr Wonnacott told TNP in an e-mail: "Our group has been patrolling the corridor for the past two years and reports any damage, fallen trees, illegal dumping or incursions into the Rail Corridor space, as well as query any construction activity that we are unaware of."
This article was first published on May 18, 2015.
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