A pebbled floor was also unearthed in the center and front of the entrance. It consisted of rectangulars and squares, surrounded by black and white diamond shaped pieces.
Most importantly, the archaeologists unearthed the upper part of a marble blocking wall.
Topped with an architrave decorated with eight-leaved embossed rosettes, the blocking wall showed a suspicious opening on its top left.
The wall, standing about 19 feet from the entrance, would conceal one or more inner chambers, the culture minister said.
The official statement doesn't explain much about the hole on the top left, which is seen by many as a strong evidence for tomb raiders plundering the tomb.
Measuring 1.6 square feet, the passage is large enough to let a small man pass through it.
According to reports in Greek media, the archaeologists looked through the window in the blocking wall and saw a second chamber and a wall in the distance, suggesting another door might lead to the tomb's interior.
At 1,935 feet wide, the mound is the largest tomb ever discovered in Greece.