Five Boston hospitals receive "suspicious" letters

Boston Poice hazmat teams were dispatched to five area hospitals today after the institutions reported receiving "suspicious looking letters," police blog and tweet.The affected hospitals are: Beth Israel Deaconess, New England Medical Center, Brigham and Women's, Boston Medical Center and New England Baptist Hospital."Preliminary investigation shows no signs of hazards on Hospital letters,"  Police tweet. "Hoax suspected, investigation ongoing."

Police tell me that what we're talking about here is letters in envelopes, not packages, and that in each case it was "just a suspicious letter, no indications that it was hazardous."

Update 4:25 p.m.
Boston police report:

At present, it appears that the envelopes received at the five locations were sent from a single source. There are no specific threats in or on the envelopes and no white powder has been detected. The sender appears to be a zealous advocate for patient’s rights and makes statements critical of the care provided by these hospitals. This investigation is ongoing and, at this time, there is no biological threat.

During the course of the investigation, no evacuations occurred at any of the locations and hospital service was never interrupted.