Washington's ongoing ricin scare just went up a notch. Politico:

A letter addressed to President Obama containing what the Secret Service calls "a suspicious substance" was intercepted Tuesday at a mail screening facility, the agency said Wednesday.
Spokesman Edwin Donovan said the letter was received at the Secret Service's White House mail screening facility, which examines all mail for the complex and is not located nearby. The facility, he said, "facility routinely identifies letters or parcels that require secondary screening or scientific testing before delivery."

There's been no confirmation that the substance in question is ricin, although sources tell ABC News that field-tests (which aren't always the most reliable) suggest that it was. The news does come one day after we learned that someone sent a letter with a substance that tested positive for ricin or a similar poison to the office of GOP Sen. Roger Wicker of Mississippi. That letter, however, was also intercepted at an off-site screening facility and never made it to Capitol Hill.

Read it at Slate.