According to information in Wikipedia, the plane had departed Ireland on the second leg of a transatlantic trip from Amsterdam to New York. After radio contact was lost, a rescue operation was launched which found light debris on the surface of the ocean. The remains of some passengers were recovered. Due to the lack of evidence, Irish and Dutch investigators could not pinpoint a probable cause for the accident. They examined the possibility of a bomb, electrical failure, or pilot error, but believed that the most likely possibility was "'overspeeding' of one of the outboard propellers resulting from oil pollution after a gear had been damaged when the supercharger of the corresponding engine was accelerated (shifted)."
The accident was the worst commercial aircraft disaster up to its time.
Church of the Brethren members, their friends and companions, who lost their lives were remembered on a memorial page of the book The Adventurous Future which included the compilation of addresses, papers, statements, and messages associated with the celebration of the two-hundred-fiftieth anniversary of the Church of the Brethren.
Sources: The Brethren Encyclopedia
The Adventurous Future