Here are two hadith about these spirits made of fire:
Hadith - Al-Bukhari 7.657, Narrated 'Aisha, r.a. Some people asked Allah's Apostle about the foretellers. He said. -They are nothing." They said, -O Allah's Apostle! Sometimes they tell us of a thing which turns out to be true." Allah's Apostle said, "A Jinn snatches that true word and pours it into the ear of his friend (the foreteller) (as one puts something into a bottle). The foreteller then mixes with that word one hundred lies."And one more:
Hadith - Tirmidhi #350 Allah's Messenger said: Don't cleanse yourself with dung or with bones for that is the food of your brothers from amongst the Jinn.