There has been speculation Alonso had some kind of medical condition in the car that caused him to lose control.
But he was certainly conscious, because he was braking at maximum force - equivalent to 75kg or more - and changing gear.
The braking appears to rule out an electric shock or another kind of seizure that would have restricted his movement. And the doctors are said by McLaren to have found no evidence of any such thing.
However, Dennis has said Alonso's team-mate Jenson Button has seen the telemetry from the car and found it unusual.
"Every single input into the car was normal," Dennis said. "Changing down gear, steering, braking… there is nothing we can see that is abnormal.
"Jenson looked at the figures and said: 'Well, that's a bit strange.' But what's a bit strange when you are wrestling with the car being destabilised by the wind?
"Yes, we can guess. Yes, we can surmise and speculate. But the only thing we can comment on is the actual facts as we know them."
One highly-experienced engineer said: "Nothing I can see in the GPS data makes me think it was anything other than him going too fast and losing control."
However, the engineer added it was "a bit odd" that Alonso would suddenly slam the brakes on in this manner if he had lost control.
