ISLAMABAD: A U.S. official has said two U.S. diplomatic outposts in Pakistan received envelopes containing an unknown white powder last week, sparking a security scare.

U.S. Embassy spokesman Lou Fintor said tests are being conducted on the substance. He declined comment Sunday on whether any embassy staffers had become ill or were under observation.

The envelopes were sent to the U.S. Embassy in Islamabad and the U.S. consulate in Karachi on Thursday and Friday. Fintor said both facilities have remained open, with no plans to close them.