Report: women's 4x100m heats – Rio 2016 Olympic Games
The defending champions, who also stormed to the world record in this event at the preceding Olympics, were seeking a safe passage through the opening round heats.
However, Gardner – running leg three – who was awaiting the baton from Felix, the seven-time Olympic medallist, appeared to set off far too soon.
In a last-ditch act to make the baton stick in Gardner’s hand, Felix desperately reached out but as she did so, the baton slipped out of her hand and fatally dropped to the track.
A protest was filed by the US team, and the referee agreed that the US runner was obstructed at the second exchange. The US team will have a re-run alone this evening in an attempt to qualify by time. The mark they have to beat is 42.70.
While the US lost their composure, Germany – who recorded a blistering world-leading time of 41.62 in Mannheim last month – laid down a statement of their medal intentions by galloping to an impressive heat two win in 42.18.
Nigeria, the fourth-place finishers in 2012, advanced to their seventh successive Olympic women’s 4x100m final in second spot in 42.55 – 0.07 clear of world bronze medallists Trinidad and Tobago.
In an error-strewn heat, host nation Brazil and Kazakhstan were also disqualified.
By contrast, heat one passed off without significant incident as Jamaica secured a routine win in a season’s best of 41.79 to edge Great Britain by 0.14.
Jamaica, seeking a first Olympic women’s 4x100m title since 2004, rolled out a quartet of Simone Facey, Sashalee Forbes, Veronica Campbell-Brown and two-time Olympic 100m champion Shelly-Ann Fraser-Pryce.
There was little to separate Jamaica and Great Britain after the first two legs but the vastly experienced double Olympic 200m champion Campbell-Brown ran a blistering final bend to put the Caribbean sprint heavyweights in control.
Great Britain, anchored by Daryll Neita, was also hugely impressive. They always kept within range of Jamaica and after stopping the clock in 41.93 – their second-fastest time in their history and within 0.12 of their national record set in London last month – they must be seen as genuine contenders to secure what would be their first medal in this event since taking bronze at the 1984 Los Angeles Olympics.
Ukraine, running from the inside lane one, produced a solid performance to clinch the third automatic spot in 42.49.
In the better quality of the two heats, Canada and China finished fourth and fifth respectively, both clocking 42.70. But if the USA runs faster than that time, China will not progress to the final.
There was disappointment for European champions Netherlands, who had to settle for sixth in 42.88 after Dafne Schippers set off too early on her leg. They will not advance.
Steve Landells for the IAAF