Online taxi service Uber Technologies Inc, which had a driver who was accused of rape in New Delhi, said it was exploring and adding new methods to verify drivers' credentials and make its service safer.

Uber has started research and development on biometrics and voice verification to build tools for enhanced driver screening, Phillip Cardenas, the company's global safety, head wrote in a blog.

The start-up was also exploring new ways to screen drivers, including polygraph tests and adding its own processes on top of commercial license verification.

“Of course, no background check can predict future behavior and no technology can yet fully prevent bad actions,” Cardenas said. “But our responsibility is to leverage every smart tool at our disposal.”

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In the United States, Uber's background-verification process includes checks of court records going back seven years; a multi-state criminal database; and the National Sex Offender Registry, according to Uber policy posted on its website. Activities that disqualify potential drivers include sexual offenses, violent crimes and gun-related infractions.

But that is not the case internationally, where records are not always kept for the same categories of data as in the United States, or treated with rigor.

“In some countries the integrity of the data can be compromised as individuals may be able to pay monetary fees to have their records adjusted,” said a spokeswoman from the National Association of Professional Background Screeners.

The San Francisco-based firm also said it was building safety incident response teams to provide round-the-clock support. Uber has been dogged by controversy surrounding its aggressive approach to local governments and traditional taxi services.

The company's business practices have come under scrutiny, with some customers alleging privacy violations, as it has grown rapidly around the world in recent months.

France, Spain and Thailand have banned some or all Uber services. The company's services have also been banned in New Delhi following the rape allegation.

Also Read: India to boost women taxi drivers, spurred by Uber rape claim

Last year, the southern state of Kerala launched 'She Taxis', a fleet of 40 pink taxis run by women, and fitted with wireless tracking gear and panic buttons linked to call centres.

Now the service has become a model for Prime Minister Narendra Modi's government to replicate nationwide, its chief executive says. “The Delhi incident shows the need for 'She Taxis' all over the country,” P.T.M. Sunish told Reuters.

'She Taxis' has ferried 24,000 people on about 10,000 trips since Nov 2013. Demand so far exceeds supply that as many as half of callers have to be turned away, Sunish said.