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: Biological features of hepatitis disappeared in all cases after cessation of the incriminated drug , while biliary , viral and immunological searches were negative .
### Output Text:
Biological features of hepatitis disappeared in all cases after cessation of the incriminated drug , while biliary , viral and immunological searches were negative . 