The workers were constructing a mining operation underground when they were hit by a high-pressure release of grout, said Bronson Mack of the Southern Nevada Water Authority, a cooperative public agency formed in 1991 to manage the water resources in a region that includes Las Vegas.

CNN: STORY HIGHLIGHTS

In the summer the RMT claimed London Underground (LU) planned to move the entire Jubilee line to driverless operation within three years, with trials starting later this year, with other lines to follow.

BBC: Strike ballot over tests for driverless Tube trains