(Reuters) - Tesla Motors Inc <TSLA.O> plans to release an update of its partly automated self-driving system "in a few weeks," Chief Executive Elon Musk tweeted on Wednesday.

Improvements to Tesla's Autopilot system, including advanced processing of radar signals, would be detailed in a blog post on the company's website later on Wednesday, the tweet said.

The National Highway Traffic Safety Administration is investigating a May 7 fatality in Florida in which a driver using Tesla's Autopilot system crashed into a truck.

Tesla’s Autopilot system uses cameras and radar, but not laser-based lidar as some other self-driving systems do. The company said its system would have had trouble distinguishing a white semi-trailer positioned across a road against a bright sky.

Musk was asked on Twitter why the vehicle's radar did not detect the truck. Musk tweeted on June 30 that "radar tunes out what looks like an overhead road sign to avoid false braking events."

In a tweet on Wednesday, Musk said software enhancements to Autopilot will be delivered wirelessly to owners' vehicles.

(Reporting by Paul Lienert in Detroit; Editing by Phil Berlowitz)