TOKYO (Reuters) - A Japanese truck driver playing Pokemon Go while driving hit two women, killing one and injuring the other, in Japan's first death related to the Nintendo Co craze.

The driver said he had been distracted by the game after his arrest for negligent driving following the accident on Wednesday evening, a spokesman for the Tokushima prefectural police said.

"The driver is still in custody. No decision has been made yet on whether to proceed with a prosecution," he added

A spokesman for Niantic Inc, which developed Pokemon GO jointly with Nintendo affiliate Pokemon Company, said the company had added a pop-up to the Pokemon Go screen when it detected an increase in speed asking for confirmation the user was not driving.

He didn't say whether the developer would take further steps to guard against accidents.

A spokesman for Nintendo offered condolences to the family of the dead woman.

"Pokemon Company and Niantic endeavor to create an environment where people can play the game safely and we will continue to do that," he added when asked whether the company would take any new measures to guard against accidents.

The popularity of augmented-reality Pokemon Go around the world has generated crowds of people in parks and other public places as user search for monsters, but has also been blamed for injuries and robberies of distracted users.

Signs at parks and other places in Japan have asked users to avoid creating a nuisance.

Pokemon incidents elsewhere have spurned warnings from authorities for users to play responsibly.

In Taiwan on Sunday Pokemon Go monster hunters caused a stampede in Taipei blocking streets in the capital. Police there have increased fines on scooter riders found playing the game in traffic.

News reports in July claimed that a Guatemalan teenager was the first Pokemon fatality after he was shot breaking into a house while playing the game.

Also in July, Pokemon Go players were robbed of their smartphones at gunpoint in a north London park in Britain, while four teens in Missouri in the U.S. used the game to target around a dozen people into armed robberies.

(Reporting by Tim Kelly; Editing by Nick Macfie)