A woman is interviewed in the SvD: She was witness to the second explosion, and when she contacted her mother, she had witnessed a car catching fire (the fisrt fire/explosion).
At the site of the second explosion the body of a dead man was found. Next to him a bag was found. According to uncomfirmed reports - but reported by all Swedish news media - the bag was full of nails!
[Sorry, links in Swedish only, "första explosionen" ´means first explosion]