Logistical arrangements made by Rio 2016 to support the samples collection process have been strongly criticised in a World Anti-Doping Agency (WADA) Independent Observers report released today.
Testing within specific sports is also highlighted as a concern in the 55-page report..
No out-of-competition testing was conducted in football, while there was "little or no" in-competition blood testing in many high risk sports and disciplines, including weightlifting.
A number of "serious failings" were highlighted in relation to the work of the Organising Committee, "some of which" were within Rio 2016’s control.
This included a loss of service due to budget cutbacks as well as "tensions" between organisers and the Brazilian Anti-Doping Agency (ABCD).
Management and staffing changes in the year before the Games was also highlighted as a problem.
A "lack of coordination or unified approach among the management team in the Rio 2016 anti-doping department during the Games itself" was another.
Problems this caused included a lack of "knowledge transfer" from previous Games, a lack of adequate training for staff and a lack of whereabouts information to find athletes during the Games.
Poor accommodation, shift-patterns and food arrangement for laboratory staff was another issue highlighted, all of which "disincentived chaperones to report for shifts and/or to stay for the duration".
One worker reportedly had to move hotels five times during the Games.
This all led to significant problems testing in the Athletes' Village, where daily targets for Out-of-Competition testing were "rarely met" and were often "only 50 per cent or less" of planned figures.
Blood testing was particularly affected after a contract to source 25 phlebotomists from a local company in Brazil to collect samples during the Games period fell through shortly beforehand.
There was not enough time to start negotiations with a new supplier.
"These various logistical issues were foreseeable and entirely avoidable, which makes their occurrence all the more disappointing," says the report, chaired by Britain's Jonathan Taylor, a lawyer from Bird and Bird, the company that also represent the International Association of Athletics Federations.
"The aggregate effect was to strain the basic sample collection process at competition venues and in the Athletes Village DCS close to breaking point, with many discrepancies observed in the sample collection procedure (even if generally the integrity of the process was not undermined, and in particular no ADRV was lost due to departures from the mandatory sample collection procedures).
"Ultimately, it was only due to the enormous resourcefulness and goodwill of some key doping control personnel working at the Games that the process did not break down entirely."
Rio 2016 officials were frequently accused of not responding to criticisms, including for their "particularly disappointing" inability to accredit additional doping control offices despite them being ready and prepared to provide assistance.
Their report did, however, praise improvements made to avoid a repeat of the alleged problems outlined in the McLaren Report into samples swapping at the Sochi 2014 Laboratory.
WADA only lifted its suspension of the laboratory 15 days before the Opening Ceremony of the Games.
It claimed that the facility was "superbly equipped, operated very securely and generally very efficiently".
It now represents an "outstanding legacy from the Games for the anti-doping movement in South America".
Other information revealed includes how 67 applications were made for Therepeutic Use Exemption (TUE) to be awarded in order to allow athletes to take substances otherwise banned.
Fifteen of these were for "substances or methods or routes of administration for which a TUE was not required, thus indicating either a "lack of knowledge or doctors playing safe.
The remaining 52 applications were granted, of which 36 were for glucocorticoids.
One was for stimulants, one for a diuretic, six for narcotics and seven for intravenous administration.
This does not include those TUE's already awarded by national anti-doping bodies.
All samples taken during the Games have now been transferred to the WADA-accredited laboratory in Lausanne, where re-testing will eventually take place.
insidethegames has contacted Rio 2016 for a reaction.
The report can be read in full here