The mother of ride-hailing firm Uber's chief executive has died in a boating accident near Fresno, California on Friday, the Fresno County Sheriff's Office said on Saturday.

Uber CEO Travis Kalanick's parents Bonnie Kalanick, 71, and Donald Kalanick were on Pine Flat Lake when their boat struck a rock and sank, it said, adding that an autopsy is planned for Sunday.

Donald Kalanick was being treated at an area hospital for what were described as moderate injuries.

Uber officials were not immediately available for comment.

The sheriff's office, however, posted a statement from Uber that read: "Last night, Travis and his family suffered an unspeakable tragedy."

"His mother passed away in a devastating boating accident near Fresno and his father is in serious condition. Our thoughts and prayers are with Travis and his family in this heartbreaking time," the statement said.

Uber has been rocked by a number of setbacks lately, including accusations of sexual harassment from a former female employee and a video showing its CEO harshly berating an Uber driver.

After posting a few tweets in 2016, Travis Kalanick has been active on the social media site this year, changing his Twitter avatar from an image of U.S. founding father Alexander Hamilton he had used for about five years with a photo of him smiling.

He also posted a photo with his parents on Twitter when they went to the Kentucky Derby together on May 6.

Reuters