Uber was slow to pull recalled cars off the road in Singapore, until one driver was in a car that caught fire, the company said.

Unlike most ride-hailing start-ups, Uber's Singapore operation owned its fleet of thousands of used cars to rent to drivers. Among them were cars from cheaper "gray market" importers, rather than authorized Honda dealers that tend to honor repair contracts, according to a story in The Wall Street Journal, which first reported it.

When some of Uber's Honda Vezel cars were recalled in April 2016 for a part that could overheat, Uber continued to buy the Vezel cars with the faulty part for eight more months, the Journal reported.

While Uber pressed its "gray market" dealer to make the repairs faster, Uber opted not to take the cars off the road, noting that it would cost about $1 million and cause panic. Instead, Uber recommended drivers get a stopgap fix that was not authorized by Honda, the Journal said.

By January 2017, one driver was in a car when it caught fire, resulting in a broken windshield and melted dashboard, but he was not hurt. Uber did not make clear that the repair was to prevent fire danger, the driver told the Journal. The Journal said all the cars have now been fixed.

In a statement to CNBC, Uber said:

As soon as we learned of a Honda Vezel from the Lion City Rental fleet catching fire, we took swift action to fix the problem, in close coordination with Singapore's Land Transport Authority as well as technical experts. But we acknowledge we could have done more—and we have done so. We've introduced robust protocols and hired three dedicated experts in-house at LCR whose sole job is to ensure we are fully responsive to safety recalls. Since the beginning of the year, we've proactively responded to six vehicle recalls and will continue to do so to protect the safety of everyone who uses Uber.

-- Additional reporting by Deirdre Bosa