Alphabet's (NASDAQ:GOOG) (NASDAQ:GOOGL) Waymo self-driving vehicle unit has now halted all operations in Detroit and Phoenix amid the COVID-19 outbreak. 

In an email obtained by CNBC, Waymo said operations in both cities have been put on hold until April 7. Last week it was reported that Waymo had suspended operations where drivers were required to be in the vehicles. On its website today, Waymo says that in Phoenix it's also now halting "our fully driverless operations within the early rider program. All driving operations in other locations also remain suspended for now, along with local delivery and truck testing."

A Waymo vehicle.

IMAGE SOURCE: WAYMO.

In the email to drivers that CNBC obtained, Waymo reportedly said that out of an "abundance of caution around the ability to operate with the safety and health of all team members" it is pausing all driving operations in both cities. Waymo noted employees won't be able to access facilities for the next two weeks. The fully driverless vehicles in Phoenix are part of a test for public ride-hailing and for local deliveries. Waymo is reportedly still paying employees for the next two weeks. The memo said managers and drivers will keep in contact and conduct meetings via digital collaboration tools. 

The move on the part of Waymo comes as Phoenix has declared a state of emergency as COVID-19, the virus caused by the novel coronavirus, spreads across the country. The city has ordered the closing of bars and restaurants and has urged residents to practice social distancing. As of Monday, there are more than 35,000 cases in the U.S. resulting in 450 deaths.  

In a tweet, when announcing the first moves last week  Waymo said "removing the human driver holds great promise not only for making our roads safer, but for helping our riders stay healthy in these uncertain times." The Alphabet unit is monitoring COVID-19 developments and will alert drivers if there are further service changes.