Last week, it came out that an Uber driver in Dallas had used a bogus, expired city permit when he applied for a job with the ridesharing service. Now, Uber is finally explaining how it failed to catch this red flag during the vetting process.

Dallas requires that all for-hire drivers — whether they are traditional taxis or new services like Uber or Lyft — get a permit from the city. Drivers can not obtain this permit if they have been recently incarcerated.

The Uber driver in question, accused of following a female passenger into her home and sexually assaulting her, had been in prison as recently as 2012 on a federal weapons conviction, and would have been ineligible for a city permit. The city claimed he used someone else’s permit that had expired in 2010.

In a letter obtained by WFAA-TV, Uber explains to the city how this driver slipped through the company’s net, in spite of supposedly beefed-up screening protocols.

The screw-up began in Jan. 2014, when the convicted felon signed up with Uber — not as a driver, but as a “partner” to help drum up business for his family’s limousine service that was on the UberBlack platform. That’s when he presented the bogus permit, but since he was listed as “Will Not Be Driving,” on the account, it appears the company did not do any further screening.

But then the real gaffe, one that would have devastating consequences, happened in April 2015, when someone at Uber “mistakenly” gave him access to be a driver for the company.

“Our internal investigation has shown that while we have strict policies and procedures, these were not properly followed,” reads the letter from Uber.

“In this instance, we failed to live up to our own high standards, for which we are truly sorry,” a company rep tells WFAA. “We are determined to learn from the mistakes that were made so we can do better in the future. Our thoughts are with the victim and her family.”‘

The controversial company then detailed steps it had taken to make sure that all remaining Dallas Uber drivers are in compliance:

• A manual review of each City of Dallas limousine permit that has been provided by either owners or drivers as a means of identification when signing up to use Uber.

• A cross-check of the City’s registered limousine drivers against our internal database to identify any abnormalities or incorrect information.

• A review to confirm that every driver or limo company owner in Dallas using the platform has been put through Uber’s background check process.

Going forward, Uber says it is introducing additional spot-checks on driver-related documents to make sure that everything is accurate and current. There will also be a new layer of driver approval in Dallas before drivers are given permission to pick up passengers.

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