Yammer RESTAPI : Post message with new line

Like if the post message type is 'announcement', there is an option 'is_rich_text' to send HTML content (like <br/> will be a new line). How do you send 'update' message with a new line from Rest API? 

Example: First line <br/> Second Line 

Expected in yammer post:

First Line

Second Line

Actual (unwanted) Result:

First line <br/> Second Line