(CNN) - The US Border Patrol's El Paso Sector had planned a "crowd control" exercise on Election Day near the port of entry in the hometown of Democratic Rep. Beto O'Rourke, who's challenging Republican Sen. Ted Cruz.
But it was postponed, according to agency spokeswoman Denisse Licon.
The abrupt postponement came after the American Civil Liberties Union and others questioned the timing of the exercise in a Hispanic enclave near the Paso del Norte Port of Entry.
"It shouldn't have taken outrage by us, congresspeople and the community for Border Patrol to know this would cause serious problems on Election Day," Terri Burke, executive director for the ACLU of Texas, said in a statement.
"These suspicious exercises scheduled in a Latinx neighborhood raise serious concerns about whether this was intended to intimidate Texans from exercising their right to vote," she said.
The national and Texas ACLU chapters, in a letter, have asked the US Justice Department to investigate what the groups called "a potential Voting Rights Act violation by the US Border Patrol."
The letter said the exercise would have taken place less than a mile from a polling location at the Armijo Recreation Center. Border patrol vehicles and armored units were observed in the area Tuesday morning before the exercise was called off, the letter said.
US Department of Homeland Security spokesman Tyler Q. Houlton said the exercise was not related to the midterm election.
"The suggestion that ongoing exercises at ports of entry in anticipation of a potential mass arrival of migrants are tied to voting by any group is flat-out wrong," said Houlton, referring to US-bound caravan of mostly Central American migrants moving through Mexico and toward the US border.
"DHS has worked tirelessly to ensure the security of our election systems and will always secure our borders regardless of what day it might be."
In a statement, US Customs and Border Protection said the "joint caravan-related exercises" were postponed "out of an abundance of caution and due to inaccurate reporting that caused unneeded confusion in border communities."
"US Customs and Border Protection has been and will continue to prepare for the potential arrival of thousands of people migrating in a caravan heading toward the United States, through the Southwest border," the statement said. "This includes training exercises, deploying additional CBP personnel and partnering with the US military."
The agency said the training exercises will continue in the coming days "to ensure border security and the safety of the American people, the traveling public, CBP personnel and the communities in which we serve."
O'Rourke, fueled by Democratic enthusiasm and a ton of cash, has given Cruz a close race.
Polls have the upstart Democrat down and Republicans believe the Republican state will come through for Cruz. But high early voting numbers and national attention on the race have given O'Rourke a chance in the contentious race.
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