WASHINGTON (Reuters) – Authorities are investigating a letter addressed to President Barack Obama after the contents preliminarily tested positive for the deadly poison ricin, the second report of such a letter in two days.

The FBI said the envelope was received at a mail screening facility outside the White House and was immediately quarantined.

WASHINGTON (Reuters) – A letter addressed to President Barack Obama contained a substance that preliminarily tested positive for the deadly poison ricin, authorities said on Wednesday.

News that the letter to Obama was being investigated came as a flurry of other reports of suspicious letters and a package caused the temporary evacuation of parts of two Senate buildings and set nerves on edge in Washington.