General Motors said Friday it is buying automated driving technology startup Cruise Automation to boost its efforts to develop self-driving cars.

Cruise, founded in San Francisco by a group of robotics experts in 2013, created an automation system for highway driving using roof-mounted modules built for installation on certain Audi models.

GM said the company would continue to work on its technology as an independent unit within the automaker's dedicated development team for automated driving.

GM did not say how much it paid for the startup, which had been funded by leading venture technology firms.

"Cruise provides our company with a unique technology advantage that is unmatched in our industry. We intend to invest significantly to further grow the talent base and capabilities already established by the Cruise team," said Mark Reuss, GM executive vice president, in a statement.

GM has been investing heavily in autonomous driving technology, as are its rivals.

It plans to launch a fleet of self-driving Chevrolet Volts at the campus of its Warren, Michigan-based technical center late in 2016.

In early January it also spent $500 million for a large stake in ride-hailing service Lyft, with an eye to eventually having Lyft drivers use its autonomous cars.