The first phantom absentee ballot request hit the Miami-Dade elections website at 9:11 p.m. Saturday, July 7.

The next one came at 9:14. Then 9:17. 9:22. 9:24. 9:25.

Within 2½ weeks, 2,552 online requests arrived from voters who had not applied for absentee ballots. They streamed in much too quickly for real people to be filling them out. They originated from only a handful of Internet Protocol addresses. And they were not random.

It had all the appearances of a political dirty trick, a high-tech effort by an unknown hacker to sway three key Aug. 14 primary elections, a Miami Herald investigation has found.

The plot failed. The elections department’s software flagged the requests as suspicious. The ballots weren’t sent out.

But who was behind it? And next time, would a more skilled hacker be able to rig an election?

Six months and a grand-jury probe later, there still are few answers about the phantom requests, which targeted Democratic voters in a congressional district and Republican voters in two Florida House districts.

The foreman of that grand jury, whose report made public the existence of the phantom requests, said jurors were eager to learn if a candidate or political consultant had succeeded in manipulating the voting system. But they didn’t get any answers.

“We were like, ‘Why didn’t anyone do something about it?’ ” foreman Jeffrey Pankey said.

The Miami-Dade state attorney’s office could not find the hacker because most of his or her actions were masked by foreign IP addresses. But at least some of the ballot requests originated in Miami and could have been further traced, The Herald found.

Prosecutors did not obtain that information as part of their initial inquiry, due to a miscommunication with the elections department.

On Friday, a day after The Miami Herald brought the domestic IP addresses to its attention, the office of State Attorney Katherine Fernández Rundle said it is reviewing them.

Under state election laws, only voters, their immediate family members or their legal guardians can submit absentee-ballot requests. Violations may be considered felony fraud.

The thwarted attempt targeted voters in three districts: Democrats in Congressional District 26, where four candidates — including a suspected ringer criminally charged Friday with federal elections violations — were vying to take on vulnerable Republican Rep. David Rivera; and Republicans in Florida House districts 103 and 112, two competitive seats.

Nine candidates were involved in the campaigns: Joe Garcia, Gustavo Marin, Gloria Romero Roses and Justin Lamar Sternad in District 26; Manny Diaz Jr., Renier Diaz de la Portilla and Alfredo Naredo-Acosta in District 103; and Gus Barreiro and Alex Diaz de la Portilla in District 112.

Garcia, Diaz and Alex Diaz de la Portilla won their primary races, all by comfortable margins. In the end, the phantom absentee ballots would not have changed the results.

But there was no way to know that at the time. And the ballots would have brought more voters into the light-turnout election. The phantom requests targeted infrequent voters who had not applied for absentees, most of whom wound up not voting in the primary at all.

Only candidates, political parties and committees have access during an election to lists updated daily showing which voters have already requested and returned absentee ballots.