Simonsen, 34, was killed when he suffered a high-speed accident at the wheel of his GTE Am class Aston Martin after running onto the kerbs through the Tertre Rouge corner just nine minutes into the race.
An investigation has been launched, with race organisers saying it would focus on the possibility the accident occurred "due to circumstances in the race".
Onboard footage from the car following immediately behind Simonsen at the time of the crash appears to show a GTE competitor ahead of him on the road going off the track in a separate incident just seconds earlier.
The fatality was the first during a race at Le Mans since Jo Gartner's massive high-speed crash in 1986. Frenchman Sebastien Enjolras was killed in a practice accident in 1997.
News of Simonsen's death threw a dark cloud over the race and marred what had been a hugely early exciting tussle between Audi and Toyota at the head of the pack.
Despite comfortably locking out the top three slots on the grid, pre-race favourites Audi were quickly under pressure from the two works Toyotas, their only serious rivals for top honours in the front-running LMP1 class.
The Audi of pole-sitter Allan McNish was beaten off the line by team-mate Andre Lotterer but worse was to come as the Scot was soon under pressure from the Toyota of Nicholas Lapierre, who passed him for second before the end of the first lap. The Toyota of Britain's Anthony Davidson was also on the move and he soon passed the number three Audi of Lucas di Grassi into the final chicane.
Davidson, whose race here 12 months ago ended in spectacular fashion when his car flipped on the Mulsanne straight, was soon on the tail of the tentative McNish and duly swept by to relegate the two-time winner to fourth place by lap two.
Simonsen's accident nine minutes into the race brought out the safety car for 59 minutes, with most of that time spent rebuilding the barriers after the stricken driver had been taken to the medical centre.
When the racing resumed, Audi soon set about asserting their authority.
With intermittent, heavy bursts of rain creating problems for the entire field, the Audis slowly crept away, with the number one car of Lotterer building a big advantage over Di Grassi and McNish, who after handing the number two car over to Loic Duval revealed just how tough conditions had been.
"It was without doubt one of the most difficult stints I've had in a car round here," McNish said.
"With the weather just spitting but changing corner to corner, it was very difficult to know how wet it was and how much you could push.
"From my point of view it was a case of not risking anything at all and just making sure we're in the race."
After their bright start, the Toyotas fell back a little from the Audi trio, with the number seven car of Lapierre losing more than a minute when he pulled over after losing drive in the first Mulsanne chicane, only to get going again within moments.
As night fell, Audi were beginning to look as though only accidents or reliability issues could trip them up, and it was the latter which struck to devastating effect with seven hours gone.
The leading number one car of Benoit Treluyer came into the pits just moment after he had struggled to make a clean getaway after a routine fuel stop.
The Audi mechanics wheeled the R18 into the garage and worked for more than half an hour - losing 12 laps in the process - to change an alternator.
The number one car eventually rejoined last in the LMP1 class.
The misfortune of the reigning two-time Le Mans winners was to the advantage of McNish, Duval and Tom Kristensen in the number two car, who inherited the lead.
With eight and a half hours on the race clock, the trio led by a lap from the number eight Toyota, with the second Toyota in third place .
The number three Audi was fourth after a series of dramas which started when Jarvis lost close to five minutes when he shed a tyre.
Although the Briton recovered to the pits for a new set of tyres, damage had been done to the car and several laps later it was back into to receive a new rear deck, new front nose and and a new right side pod.