A week after the accident, some questions remain unanswered. Let's look at some of them.

The Eastern Star is hoisted from the water after it sank in Yangtze River, June 5. [Photo by Chen Zhuo/Asianewsphoto]

1. Did tornado sink the boat?

After the disaster struck, the China Meteorological Administration claimed it capsized after being caught in a tornado. But later, the "tornado claim" was questioned when some experts said there was no solid evidence that a tornado caused the accident.

So was it the tornado?

According to Xue Feng, a researcher with atmospheric physics institute of the Chinese Academy of Sciences, if the tornado is small in size then sometimes radars and weather stations are unable to pick it up.

Another possibility is that the tornado occurred and perished on the surface of the river, leaving no trace on the bank, said Xue.