Petacchi (right, in pink) took advantage while others were caught up in crashes
Italian Alessandro Petacchi won a sprint finish into Brussels on the first stage of the Tour de France after a chaotic finale marred by crashes.
Mark Cavendish was unable to contest it after being involved in the first crash before a huge pile-up 500m from home.
The Manxman's lead-out man Mark Renshaw ended up taking second place ahead of Cavendish's green jersey rival, Norwegian Thor Hushovd, in third.
Swiss Fabian Cancellara retained the yellow jersey after his prologue win.
A philosophical Cavendish, who is hoping to add to his 10 stage wins in the race, declared himself "OK" after the incident, adding: "It is just life, isn't it?"
He declined to expand further on his part in the first of the three incidents in the final 3,000m, but his HTC-Columbia team-mate Tony Martin - who retained second place overall - defended Cavendish's part in the crash.
"There was a little crash on the last right-hand corner with 1km to go and I think he was just behind it so he had no chance to go for the sprint," said the German.
"Maybe he will be a bit angry but I think that is good - he will get stronger and stronger and we will try again tomorrow."
The veteran Petacchi, who took his fifth Tour stage win, and his first since 2003, said: "I'm not sure that Cavendish could beat me today if he had been there, because I really did a good sprint."
The opening road stage of this year's Tour de France got under way in Rotterdam with the riders rolling over the Erasmus Bridge and through the streets of the famous port town.
Within metres of the official start, an attack by Dutch rider Lars Boom (Rabobank) saw him go clear of the main bunch with Maarten Wynants (Quickstep) and Alain Perez (Euskatel). The three were allowed to escape by the field and quickly established a lead that stretched to over seven minutes at its peak.
Millar and Basso were among those brought down by a stray dog
Behind them a nervous peloton remained grouped despite the strong North Sea crosswinds which it had been predicted would cause splits. Instead it was a family pet that caused the first major incident of the race when a dog ran into the road, bringing down Britain's David Millar (Garmin-Transitions) and yellow jersey contender Ivan Basso (Liquigas).
Both riders rejoined the bunch unharmed and it continued to rein in the break as it headed towards the Belgian border where the riders were greeted by huge crowds which lined the route. Among the other riders to fall on the stage, Adam Hansen (HTC-Columbia) was the worst injured with a broken collarbone which did not stop him finishing the stage.
As the race crossed the cobbled streets of Mechelen with 32km to go, the Belgian Wynants attacked his breakaway companions, and was joined by the Moldovan champion, Alexander Pliuschin. The pair stretched their lead to one minute but were never likely to stay away from a peloton set on a sprint finish.
With 15km remaining several teams fought for control of the peloton with Lampre, Cervelo, Garmin and HTC-Columbia all vying to position their sprinters for a sequence of tight turns which would be instrumental in the final result.
Bert Grabsch (HTC-Columbia) ran wide into one corner before a tight right-hand corner saw Cavendish drift from his line on the inside, taking both himself and Oscar Freire out of contention for the stage in a crash that also involved another Briton, Jeremy Hunt (Cervelo).
As riders attempted to re-organise themselves in the final straight, another crash in the middle of the bunch brought the majority of the field to a standstill. This left a group of around 30 riders to contest the sprint, including Cavendish's green jersey rivals Hushovd, Farrar and Petacchi.
Lloyd Mondory gestures after being brought down in the third crash
A further crash in the closing metres saw Farrar also ruled out and AG2R-La Mondiale's Lloyd Mondory angrily gesturing as he was separated from his bicycle. Petacchi was able to stay ahead of the incidents to finish ahead of Renshaw and Hushovd.
The crashes occurred within the final three kilometres, meaning that the riders involved were all credited with the same time as the winner. As a result Cancellara - who was also caught up in the biggest crash near the finish - retains the yellow jersey with a 10-second lead over Martin and 20 over Britain's David Millar in third.
"Right after the crash I tried to brake but then I somersaulted over the handlebars and landed on the tarmac," said Cancellara, who won Saturday's prologue in Rotterdam.
"I didn't feel anything at the time but my whole left side is sore now. It was madness all day.
"There were millions of spectators along the route which made it a great opening day but also a very nervous day for everyone with so many spectators so close on both sides.
"It was a long day as well and it might have been that the crashes were down to a loss of concentration because of that."
"However well prepared you are, an accident can ruin the best-laid plans. The absence of Cavendish and Tyler Farrar in the sprint finish in Brussels means we still have no inkling of who is the fastest man in the Tour this year," said BBC Radio 5 live commentator Peter Slater.
On Stage Two, the riders will face a different challenge as the race heads through the Ardennes and over climbs familiar from the spring races Flèche Wallonne and Liège-Bastogne-Liège.
Stage One result:
1 Alessandro Petacchi (Ita/Lampre) 5 hours, 9 minutes, 38 seconds
2 Mark Renshaw (Aus/HTC-Columbia) same time
3 Thor Hushovd (Nor/Cervelo) same time
4 Robbie McEwen (Aus/Katusha) same time
5 Matthieu Ladagnous (Fra/FDJ) same time
15 Geraint Thomas (GB/Team Sky) same time
For full results visit
the official Tour de France site
1 Fabian Cancellara (Swi/Saxo Bank) 5 hours, 19 minutes, 38 seconds
2 Tony Martin (Ger/HTC-Columbia) +10 seconds
3 David Millar (GB/Garmin) +20"
4 Lance Armstrong (USA/Radioshack) +22"
5 Geraint Thomas (GB/Team Sky) +23"
6 Alberto Contador (Spa/Astana) + 27"
75 Bradley Wiggins (GB/Team Sky) +56"
110 Steve Cummings (GB/Team Sky) +1'07"
123 Charly Wegelius (GB/Omega) +1'10"
124 Mark Cavendish (GB/HTC-Columbia) +1'10"
136 Jeremy Hunt (GB/Cervelo) +1'13"
173 Daniel Lloyd (GB/Cervelo) +1'23"