The German lost control of his SF90 at Turn 3 during the morning session, and the car ploughed into the barriers on the outside of the corner.
Footage of the incident showed that some kind of failure at the front left of the car triggered the crash, but it took detailed analysis by Ferrari engineers to confirm that the problem was with the wheel rim.
A statement issued by Ferrari on Thursday said: “After thorough checks we found that Seb’s off yesterday was due to a rim issue.
"The rim had been damaged a few seconds before by an impact with a foreign object.”
Vettel escaped unscathed from the incident, but was briefly checked by medical staff at the circuit as a precautionary measure.
He had feared that the damage caused by the impact would make it impossible to find the cause of the crash.
“By the feeling, there was an issue with the front left corner,” he said. “From there, there was nothing I could have done to avoid the impact.?
“I wasn't in control anymore and went more or less straight into the barriers."
As the result of the lost track time on Thursday, Ferrari reshuffled its testing programme for the final days of the test.?
Charles Leclerc and Vettel are now getting a whole day each rather than splitting the two days as had been previously planned.