Waymo has paused its driverless car services in five US cities, including Atlanta and four cities in Texas, after a software bug sent vehicles into flooded roads where they got stranded.

The company paused its services in Atlanta, Georgia, as well as in four cities in Texas, "out of an abundance of caution" after an unoccupied Waymo robotaxi got stuck in flood water.

Waymo also recalled nearly 3,800 robotaxis earlier this month after identifying a software problem that could cause vehicles to enter flooded roads with higher speed limits, following an incident in San Antonio, Texas, on April 20th.

“We have temporarily paused freeway operations as we work to integrate recent technical learnings into our software and expect to resume these routes soon,” a Waymo spokesperson said in an email, according to Reuters.

Services in San Antonio are paused until the software fix is rolled out.

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A spokesperson from Waymo, which is owned by Google’s parent company Alphabet, told the BBC that "mitigations" had already been put in place, such as "limiting access to areas where flash flooding might occur".

The issue adds to ongoing scrutiny of Waymo's vehicle safety. During a two-hour Senate Commerce Committee hearing in February, Waymo acknowledged that its robotaxis sometimes rely on live human guidance from overseas operators.

Waymo CSO Dr. Mauricio Peña explained that the human agents were only there to “provide guidance” to the robotaxis.

“They do not remotely drive the vehicles. Waymo asks for guidance in certain situations and gets human input. But the Waymo vehicle is always in charge of the dynamic driving task,” Peña said.

The admission came a few weeks after a Waymo robotaxi struck a child outside an elementary school in California on January 23rd, triggering a safety review.