In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: There have also been two reported fatalities from DM overdoses ( Fleming 1986 ) .
### Output Text:
There have also been two reported fatalities from <span class="chemical">DM</span> overdoses ( Fleming 1986 ) . 