LOS ANGELES—Federal safety regulators are sending a team to California to investigate a fatal freeway crash involving a Tesla, just after authorities near Oakland arrested a man in another Tesla rolling down a freeway with no one behind the steering wheel. Experts say both cases raise pressure on the National Highway Traffic Safety Administration to take action on Tesla’s partially automated driving system called Autopilot, which has been involved in multiple crashes that have resulted in at least three U.S. deaths. The probe of the May 5 crash in Fontana, California, east of Los Angeles, is the 29th case involving a Tesla that the agency has responded to. “The details of whether the Tesla was in autonomous mode are still under investigation,” Officer Stephen Rawls, a spokesperson for the California Highway Patrol, said in an email Wednesday. The Tesla driver, a 35-year-old man whose name has not been released, was …