A recent wave of letters containing a white powder has alarmed public officials in Kansas, who are working with state and federal agencies to investigate the source and nature of the substance.

The Kansas Bureau of Investigation said it has received about 100 letters so far, mostly addressed to Republican lawmakers at their homes.

The letters have a cryptic message that reads “it’s important not to choke on your ambition” and are signed by “your secret despirer”.

Preliminary tests have shown that the powder is not a common biological agent, but further analysis is needed to determine its composition and potential harm.

No one has been injured by the letters, but authorities are urging caution and vigilance for anyone who receives a suspicious package.