However, no further updates to the preliminary results were made after 19:40 hours, local time, on election day, which caused consternation among opposition politicians and election monitors deployed by the Organization of American States (OAS); Mesa described the suspension as "extremely serious" and spoke of manipulation; the OAS requested an explanation for the pause in the publication of the vote tally. But while the vote tally was not being publicized, the election staff were still observed counting votes overnight.
After the publication of the count resumed, the OAS said it observed a "drastic and hard-to-explain change in the trend", and recommended a runoff election due to what the OAS viewed as manipulation.
Although a complete report was not yet due, mounting tension in the country prompted the OAS to release a preliminary report on 10 November concluding that they had discovered sufficient evidence of election fraud to warrant new elections. This led to a string of events culminating in the resignation of Morales. The OAS uncovered multiple irregularities, including failures in the chain of custody for ballots, alteration and forgery of electoral material, redirection of data to unauthorized servers and data manipulation.
They added that it was statistically unlikely that Morales had secured the 10-percentage-point margin of victory needed to win outright, saying that election should be annulled after it had found "clear manipulations" of the voting system, and that "The manipulations to the computer systems are of such magnitude that they must be deeply investigated by the Bolivian State to get to the bottom of and assign responsibility in this serious case."
On 5 December, the full 95-page OAS report was released along with 500 pages of corroborating details as appendices. These included that an outside user who controlled a Linux AMI appliance with "root privileges" — conferring the ability to alter results – accessed the official vote-counting server during the counting and that in a sample of 4,692 returns from polling stations around the country, 226 showed multiple signatures by the same person for different voting booths, a violation of electoral law. On those returns, 91 percent of votes went to MAS, approximately double the rate recorded elsewhere.
