Is It Poltergeist Activity?

This is a story which I have been hearing from a very young age. It was experienced by my maternal uncle. First of all, he is a very bold person. When there was a rumour of ghost sightings around my house, he was awake all night to find out. He never believed in ghosts, until he had this particular experience.

He was working in a baniyan exports company in Tirupur, which happens to be my hometown. He used to work late nights. It is a two-storeyed building with company above and the godown with large bales of cotton stacked below. People working in the godown reported that at 11 at night, they heard sounds of stone falling. When my uncle and others went to investigate, they saw stones of golf ball size thrown across the room. They were coming from the area behind the high stacks of cotton. There were no windows or doors that side (only 1 door on the opposite end) through which the stones might have come.

They rushed to the place from where the stones fell to find nothing. When they returned to the other side, the activity started again. None could tell how the stones came in the closed place. It was his first personal experience... Nothing more happened there.

Then one day in our grandma's house, the vel (holy weapon) kept in the pooja room (it was mounted on a mixer jar) started moving by itself. It was as if someone was moving it like playing with a doll taking careful steps. It was not a slopy surface and it did not fall while walking.

Another experience was when my uncle was burning a metal plate. He threw it in fire and stepped back. Suddenly his hand caught fire. It was like something came out of the fire and grabbed his hand.

Whatever the thing behind these happenings, I seek to find a logical explanation. This is my second story and I personally appreciate varied comments.