Footage appears to show a police van following an electric bike just minutes before two teenage boys died a crash that sparked riots in Cardiff.
Best friends Kyrees Sullivan, 16, and Harvey Evans, 15, both died in the accident, which reportedly took place while they were riding an electric bike.
The deaths were met with outrage and turned the Cardiff district of Ely into what was called an "absolute war zone".
Police were swift to offer condolences to the families of the two dead teenagers but the disturbances were called "appalling and completely unacceptable" by Downing Street.
More than 150 youths fought pitched battles with the police and terrified residents watched as their cars were turned over and set alight. As many as 15 officers were injured.
The video has been time-stamped to 17:59 on Monday on Frank Road in Ely, 900m away from the site of the suspected crash, reported the BBC.
Violence unfolded on Monday night amid rumours spread on social media that Kyrees and Harvey had been killed in a police chase.
Cardiff Chief Superintendent Martyn Stone said that an investigation is studying the video appearing to show a police can pursuing an electric bike but denied there was a police vehicle on the road when the accident happened.
"There is CCTV footage showing a police vehicle following a bike recorded which will be part of the investigation and will assist in understanding the circumstances of the collision," he said.
But he added that there was no police vehicle on the road when the collision happened.
He stated: "South Wales Police is continuing to investigate a fatal road traffic collision and serious disorder which happened in the Ely area of Cardiff last night.
"At 6.03pm yesterday we received a report of a serious collision on Snowdon Road which tragically resulted in the deaths of two teenage boys.
"The families of the two boys are being supported by family liaison officers and our thoughts are with both families at this terrible time. An electric bike has been seized from the scene and enquiries are on going to establish the exact circumstances."
It comes after South Wales Police and Crime Commissioner Alun Michael reportedly said that a chase did not take place on Tuesday morning.
He told BBC Radio 4's Today programme: "My understanding is that there was a road traffic accident involving two teenagers.
"That appears to have sparked, for reasons that aren't clear, the disorder that you've referred to.”
