SHENYANG, Feb. 6 (Xinhua) -- An ancient tomb with a special drainage system and a fresco has been discovered in northeast China's Liaoning Province, local archaeological authorities said Tuesday.

The excavation of the tomb site in Xinli Village of Beizhen City was approved by the State Administration of Cultural Heritage in June 2017.

Archaeologists found a fresco that had been painted three times, in one tomb. The first two drawings were hard to identify as they were very vague. Vehicles, horses, camels and figures can be recognized in the third.

"The owner of the tomb hasn't been identified at this moment, but it may belong to an aristocrat of the Liao Dynasty (916 - 1125). It also could be a joint burial tomb as the fresco had been painted three times," said Si Weiwei, a researcher at the provincial cultural relics and archaeological institute.

Experts have speculated that the construction of the tomb was finished and the fresco completed before the owner died. When the owner died, the fresco may have been refurbished and after his or her spouse died, the fresco painted a third time.

Meanwhile, archaeologists also discovered a complete drainage system surrounding the tomb. The drainage ditches were filled with many stone balls, which are rarely found in Liao Dynasty tombs.

"The function of those stone balls is to drain away water, on the one hand, and also to prevent tomb raiders, on the other hand," Si said.

Based on the shape of the tomb and objects excavated, archaeologists said it could be a family joint burial tomb from the middle or late Liao Dynasty.