The thumb drives and a laptop went missing some time this week, but exactly when remains unclear, the Philadelphia Inquirer reported Wednesday.
“We are confident that this incident will not in any way compromise the integrity of the election,” a spokesman for City Commissioner Lisa Deeley told the paper.
Deeley’s office also said once set up, voting machines are sealed – so authorities were reexamining them to see if they had been tampered with.
But the paper also reported that city commissioners had been reluctant to confirm the thefts and privately worried that the thefts could lend credence to claims of threats to election integrity.
The voting machine manufacturer, Election Systems & Software, said the USB drivers are encrypted and have “multiple levels of security,” CBS Philly reported.
Each of the drives is matched to a single voting machine, according to the Inquirer, and inserting the wrong device will result in an error. Any machines at risk of having been tampered with would be wiped clean and re-tested.
The company also blocked network access to the stolen laptop and changed the owner’s passwords.
“ES&S is confident that this incident will not in any way compromise the integrity of the election,” the company said.
Early voting is already underway, with 17 “satellite election offices” open in Philadelphia seven days a week, according to the mayor’s office.
The incident comes about a week after another election issue in the city.
Deeley had asked Pennsylvania’s GOP-controlled state Legislature to eliminate a rule requiring special envelopes for mail-in ballots over concerns that tens of thousands of votes could be discarded with the rule in place.
Pennsylvania is one of 16 states that still require a secrecy envelope, and Deeley said it “exists now only as a means to disenfranchise well-intentioned Pennsylvania voters.”
Fox News’ Vandana Rambaran contributed to this report.