Martin Luther King Jr. -- Family in Accident After Rally at Memorial

Martin Luther King Jr.'s family just got into an auto accident while leaving the rally to commemorate the 50th anniversary of his "I have a dream" speech ... TMZ has learned.

According to sources on the scene ... several of MLK Jr.'s siblings and grandchildren were on a charter bus leaving the rally when a van ran a red light ... forcing the bus driver to slam on the brakes to dodge the vehicle.

MLK's sister -- Christine King Farris -- was on the bus at the time of the accident. Earlier in the day, the 85-year-old placed a wreath on the MLK Jr. Memorial.

Farris was joined at the wreath ceremony by MLK's daughter Bernice King.

We're told Bernice was not on the bus at the time of the accident.

We're told Omarosa Manigault was on the bus with the family ... and hit her head on the seat in front of her, but she's okay.

We're told the bus driver was transported to a nearby hospital.

Omarosa tweeted after the crash -- "Yikes just got banged up a lil bit on bus- I am ok! #HitMyHead ouch"