Mexico City - Giant Motors, an automaker partially owned by Mexican billionaire Carlos Slim, is working on a prototype electric taxi to replace the gas-guzzling cabs polluting Mexico City's air, a company executive said.

Giant has partnered with electric vehicle maker Moldex, a unit of Mexican breadmaker Grupo Bimbo, and four Mexican universities to produce the environmentally friendly car that will eventually replace part of Mexico City's more than 130,000 registered cabs, said Elias Massri, chief executive of Giant Motors Latinoamerica.

"We're developing the prototypes and hope to finish them this year to find a viable solution, an electric vehicle, that genuinely replaces gasoline-using cars," Massri said in an interview last week.

A thick haze periodically descends on Mexico City, the Western Hemisphere's largest megalopolis, irritating eyes and throats and prompting authorities to issue health warnings and force cars off the streets. Air quality in Mexico City, home to an estimated 5.4 million vehicles, has been particularly poor in recent weeks.

"The peculiar challenge with taxis in Mexico City is that they often ride around with no passenger, looking for a fare," said Massri. That means the electric taxis need to boast fast-charging batteries that can last, he added.

Over the last few years Giant Motors and Moldex have developed and sold 500 light-weight, electric cargo trucks capable of handling up to a one tonne load. Massri said the experience has given them a platform for the taxi project.

Slim's Grupo Financiero Inbursa has a 50 percent stake in Giant Motors.

In February, Giant Motors and China's Anhui Jianghuai Automobile Group Co Ltd, along with distributor Chori Co Ltd, said they would invest some $210 million to build SUVs at a plant in the central state of Hidalgo.

Giant Motors and JAC aim to be producing some 10,000 vehicles per year at the Hidalgo plant within four years, said Massri. Passenger cars will account for 70 percent of total output and the remainder will be commercial trucks.

Initially, the Giant Motors-JAC Motors joint venture will focus on selling to Mexico's growing domestic market, with an eye to expanding into other Latin American nations, Massri said.