MUMBAI, India — When it was launched less than a year ago, the $2,500 Tata Nano was promoted as a safe, ultra-cheap car for poor Indians, an alternative to the motorbikes that zoom precariously around the country.

New questions about the safety of the pint-sized auto are being raised, however, after one of them burst into flames Sunday as it was being driven home from the showroom.

Software engineer Satish Sawant, his wife and 5-year-old son escaped from the silver Tata Nano – which still bore a celebratory garland of marigolds on the hood – before the tiny car was engulfed by fire.

A chauffeur initially was at the wheel, but Sawant said he had taken over driving before the fire broke out. Tata has offered Sawant a replacement Nano or a refund.

“My wife now doesn’t want to buy any car,” Sawant said by phone from his home in northern Mumbai on Thursday. “She doesn’t even want to go for a Mercedes.”

His ordeal was an example of the latest problem with the Nano as Tata Motors sets its sights on global expansion and aims to ramp up production with a new factory next month.

Tata spokesman Debasis Ray said the company is investigating the cause of the fire. Although Ray said the automaker believed it was “a one-off, stray incident,” he also said he did not know how the fire began.

Last fall, three customers in India complained that their Nanos started smoking, but Ray said Thursday the incidents are not related to this week’s fire.

Tata Motors attributed those to a faulty electrical switch and said it had changed suppliers and done additional tests to rule out a recall or redesign.

The Nano has gotten rave reviews and awards, but some say the smoke and fire problems are symptomatic of pervasive quality control issues at India’s No. 3 carmaker.