The door of a Muni Metro car spontaneously fell off while the train was in motion on Tuesday evening between Castro and Church Street stations, on the inbound track. Muni rider James Chang took the photos above and posted them to Twitter, saying that train halted after the door came off, but the "driver didn't make any announcements," and after some time passed the "impatient" passengers all walked off the train through the tunnel to Church Street. There were no injuries.

The incident happened just after 7 p.m., and there were reportedly 14 passengers on board the T-Third train at the time.

The Examiner confirmed the details of the incident with the SFMTA's director of transit, John Haley, and he tried to play it off as a great rarity. "It’s more common than being hit by a meteorite, but not much more."

The problem stemmed from a worn out "end cap" on the door slider's channel, and Haley said that this part would become part of the routine inspections done on every car every 10 weeks.

But the aging fleet of Breda cars on the Muni Metro lines could be cause for some ongoing concern, and SFist reached out to Muni spokesperson Paul Rose regarding a seeming uptick in issues with train doors that were leading to disabled trains and delays. No further information on the frequency of these issues came our way, and I've reached out again seeking the data.

As you may know, Muni is due to get the first cars in its newly manufactured fleet sometime this year, with the first ones having started testing in January. Haley tells the Examiner that these new cars, manufactured by German company Siemans, have sturdier door mechanisms.

Chang, who witnessed Tuesday's incident, tells the Ex that things could have been far worse if that had actually been a peak-hour train traveling at 35 miles per hour. "If this were a crowded train during rush hour, there is a good chance people would have fallen out and been injured or killed."

Related: Muni Is Getting A New Fleet Of Train Cars, Starting This Year