The private operator responsible for running Sydney's public buses will conduct an internal investigation after a bus driver who allegedly caused a crash that left two scooter riders dead was charged with dangerous driving and subsequently stood down from driving duties.

Police allege the bus driver, 48-year-old Luis Rojas, was using a mobile phone behind the wheel as his bus travelled south along Kingsgrove Road in Kingsgrove on Monday night. About 8.20pm, the bus struck a stationary scooter carrying two men, sending it into the path of an oncoming car.

A bus driver has been charged over a crash that left two men dead in Kingsgrove on Monday night. Credit:TNV

Despite the efforts of paramedics and Fire and Rescue NSW crews at the scene, the 32-year-old driver of the scooter and his 28-year-old passenger died on the road.

"Unfortunately the rider was thrown into the path of another vehicle and was killed instantly, and the passenger died a short time later," Assistant Commissioner Michael Corboy of Traffic and Highway Patrol said.