A Tesla fire in Los Angeles last week is drawing attention again to the safety of the cars' lithium-ion batteries.

British television and stage director Michael Morris drove his Tesla Model S on Santa Monica Boulevard in West Hollywood when a couple in another car flagged him down and told him to pull over, according to a Tweet by his wife, actress Mary McCormack.

McCormack captured and shared a video with flames shooting from beneath the Tesla. Morris exited the car before it was engulfed in flames, and no injuries were reported.

So far, the cause of the fire isn't clear, although police are investigating the battery. Several lithium-ion batteries in Tesla Model S's caught fire after crashes or after the cars ran over debris in the road in the first two years after the car went on sale in 2012. Since then, Tesla has reinforced the cars' undercarriage to better protect the battery packs and adjusted the car's air suspension.

Tesla told the BBC that it is conducting its own investigation into what happened and offered to support authorities. 

In a separate Tweet, Morris said his car was an "ordinary Tesla, not one with Autopilot," referring to several recent crash when Tesla's Autopilot auto steering and adaptive cruise-control system were engaged during accidents. There was no crash involved in this latest fire.

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In a 2016 study, Swedish researchers found that Teslas had a rate of fires of about 1 in 20,000 cars, compared with about 1 in 1,000 fires for gasoline-powered cars, though they note that this includes all types of fires in gas cars, including some that were set intentionally.

Some scientists have criticized the use of lithium-ion batteries in cars, because their chemistry is not as stable as some would like. Automakers have adopted various safety strategies to minimize the risk.

The ultimate solution would seem to be solid-state batteries, which Japanese and American scientists are working to develop.