The White House received a potentially deadly letter this week — post laced with cyanide — according to the Secret Service Tuesday.

A spokesman for the federal law enforcement agency explained in a statement that the letter was received at the White House Mail Screening Facility Monday where an initial test for the poisonous chemical compound turned up negative. However, the second round of testing provided a “presumptive positive for cyanide”. The sample was then shipped over to another facility for further testing.

No one was injured or exposed to any hazardous material during the incident.

As reported by The Intercept, the man linked to the return address on the letter has had a long history with the Secret Service. They’ve been familiar with him since 1995, when he sent a package to the White House covered in feces and urine.

CNN