Water from RO purifier smells like kerosene when kept in a bottle - What can the reason be and what should be done now ?

Hi,

I have a Kent RO system and water from it, when kept in a plastic bottle, smells like kerosene. Can somebody please help us and tell us why this happens? I bought a TDS meter and it shows 40 to 50ppm value. The Kent service engineer could not rectify. I have a 2 year old kid and would like to take all possible precautions.

Thanks