Amazon contract delivery drivers in Chicago are allegedly hanging their smartphones outside warehouses and delivery points to boost their chances of getting delivery orders.

Major news outlet Bloomberg last week reported on a strange new trend among Amazon and Whole foods contract drivers in Chicago – hanging their smartphones in trees close to the companies’ warehouses and parking their cars nearby to get first dibs on accepting new delivery orders.

Amazon’s system allegedly chooses drivers based on who is closest to the pickup location, so even the slightest advantage over the stiff competition among drivers can boost chances of getting access to the offers first.

The phones in the trees have the Amazon Flex app installed and are synched with other phones belonging to other drivers, to make it harder for Amazon to detect offenders.

“The phones in trees seem to serve as master devices that dispatch routes to multiple nearby drivers in on the plot, according to drivers who have observed the process,” Bloomber writes.

“They believe an unidentified person or entity is acting as an intermediary between Amazon and the drivers and charging drivers to secure more routes, which is against Amazon’s policies. The perpetrators likely dangle multiple phones in the trees to spread the work around to multiple Amazon Flex accounts and avoid detection by Amazon”

A driver who has observed the phones hanging in trees outside various Amazon and Whole Foods locations in Chicago said the retail giant knows about the practice “but does nothing” about it. However, an Amazon spokesperson told Business Insider that the Bloomberg story is inaccurate and that the alleged cheating tactic is not very effective.

“This story isn’t an accurate description of how they work, and waiting in the parking lot or using the store Wi-Fi is not an effective way to increase one’s chances of seeing an instant offer,” the spokesperson said.

An internal email obtained by Bloomberg allegedly showed that Amazon had been notified of the practice by other drivers, but while it promised to investigate, the company said it wouldn’t be able to share the results of that investigation.

The trend of hanging phones in trees near Amazon pick-up location is being viewed as further proof of the cutthroat competition among ride sharing and delivery contract drivers.