- South Wales Police said it was called to the scene of the fatal crash on Snowden Road shortly after 18:00 BST on Monday.
- "So obviously there's going to be investigations going on this morning to try and establish what happened", Mr Michael said.
Two teenage boys died in a crash before a riot broke out in Cardiff which left several police officers injured.
Cars were set alight and fireworks thrown at police as 100 to 150 people gathered at the scene in Ely on Monday.
Police dismissed social media rumours that they were involved in the crash, saying officers arrived at the scene afterwards.
The link between the crash and the disorder was unclear, South Wales' police and crime commissioner said.
"It would appear that there were rumours, and those rumours became rife, of a police chase - which wasn't the case," Alun Michael said.
"And I think it illustrates the speed with which rumours can run around with the activity that goes on on social media nowadays - and that events can get out of hand."
Mr Michael said up to 12 officers had been injured in the disorder.
South Wales Police said it was called to the scene of the fatal crash on Snowden Road shortly after 18:00 BST on Monday.
At around 20:00 BST, police tweeted that they were working to manage the collision but also to de-escalate ongoing disorder at the scene.
The force said it received a large number of calls from "understandably frightened" residents.
By 01:10 BST on Tuesday, police said a number of vehicles had been set alight and arrests were being made.
The force said its thoughts were with the families of the two boys who had died as well as those affected by the subsequent disorder.
More arrests would follow, a police spokesperson said.
"Our focus now is to fully investigate the circumstances of the collision and the appalling scenes that followed".
Mr Michael told BBC Radio 4's Today that the crash in which the two teenagers died was "being investigated in its own right", but that it appeared to have sparked the disorder.
But he said that the connection between the two events was "far from clear".
"So obviously there's going to be investigations going on this morning to try and establish what happened", Mr Michael said.
Ely is an estate on the western side of Cardiff, roughly 5 miles (8km) from the city centre.
The vicar of Ely said something has been "simmering" in the area for some time.
Canon Jan Gould told BBC Radio 5 Live's Nicky Campbell: "It is not uncommon in the summer to hear helicopters keeping an eye on things. It is becoming more and more of a problem."
She added: "My heart bleeds for Ely."
Two police cars were damaged in the disorder, with pictures showing one with its windscreen broken and its wing mirrors hanging off.
A member of the public was also attacked because some of those gathered thought they were an undercover police officer, according to one of the senior officers at the scene.
At least two parked cars were set alight, one of them after being tipped onto its roof.
Jane Palmer said she and her family watched from a window as people outside set fire to her car.
"I'm disabled so now I'm trapped without my car," she said.
"Why are they doing this? It's just silly now."
Wales' First Minister Mark Drakeford said he was "very concerned" by the "upsetting reports" from Ely overnight.
"We continue to monitor the situation to gain a fuller understanding of the circumstances," Mr Drakeford said.
As the disorder continued into the early hours of the morning, those gathered moved down nearby Highmead Road as police attempted to disperse them.
Police, including officers on horseback, were seen outside Ely police station amid suggestions that it could be targeted.
John Urquhart, who lives in Ely, witnessed the incident escalate from the start of the evening.
He said the vast majority of people were in the street because they "wanted to know what would happen next", and added that there was "a very small number of people actually doing any sort of violence."
Mr Urquhart said he was very "counter-violence" and offered first aid to people during the evening.
Another resident, who did not want to be named, said those behind the violence were "kids", and that it had "crossed a line" and "needs to stop".