The caves contained a mass collection of graves and the walls were painted with drawings of people with elongated heads. Also there were images of the sun, moon, and stars. The expedition archaeologists uncovered the graves and discovered the remains of ancient beings.
The skeletons were a small four feet tall, with abnormally giant skulls. Inside of the tombs a collection of stone disks were discovered. The disks were twelve inches in diameter, with a hole in the middle.
The objects had a groove on the surface of the disk and spiraled outwards from the middle hole forming a double spiral. Closer inspection showed that the grooves were actually a line of small symbol like etches.
For twenty years the Dropa stones were said to have sat in storage before they were given to Tsum Um Nui (楚聞明) for study in 1958. It is said that he came to the conclusion that the grooves on the discs were actually very tiny hieroglyphs, none of which were of a pattern that had been seen before, and which can only be seen with the use of a magnifying glass. By 1962, he had allegedly deciphered them into a story that told of a spacecraft that crashed landed in the area of the cave, the Bayan Har Shan region and that the ship contained the Dropa people who could not fix it and therefore had to adapt to Earth. Further, his research claims that the Dropa people were hunted down and killed by the local Ham tribesmen for a period. Tsum Um Nui noted specifically that one glyph apparently said "The Dropa came down from the clouds in their aircraft. Our men, women and children hid in the caves ten times before sunrise. When at last we understood the sign language of the Dropas, we realized that the newcomers had peaceful intentions".
Tsum Um Nui is said to have published his findings 1962 in a professional journal, and was subsequently ridiculed and met with disbelief. Shortly afterwards he is said to have gone to Japan in a self-imposed exile where he died not long after he completed the manuscript of his work. http://en.wikipedia.org/wiki/Dropa_stones
I am not sure whether this information is true or precise, but with so many other supposed cover ups, it sort of disturbs me that something so big can be kept from humanity by the powers that be. Whats the point of keeping it so secret? Will it change humanity? I believe it would change some things but I also believe mankind is ready for that change.
There are several countries that have done research on the dropa stones, and that information can be found at WikiPedia using the links above. There are also several other articles and blogs that give much detail on these stones. The following website is a detailed and very easy read about the dropa stones.