Police were called to The New York Times on Friday after the newspaper received an envelope containing a suspicious-looking powder.

A worker opened the envelope, which contained a "white powdery substance," at about 12:30 p.m. It was not immediately known what the substance was.

Police and a Times spokeswoman, Catherine Mathis, said the envelope also contained an editorial with an "X" through it.

Mathis said the worker followed the newspaper's security protocol by putting the envelope in a plastic bag and calling police.

The employee was taken to a hospital to be examined, but was showing no symptoms or injuries, Mathis said.

The building's eighth floor was evacuated and sealed off as the police hazardous materials unit conducted tests. The worker who opened the envelope was isolated, although he appeared to be unharmed, police said.

The envelope, hand-addressed to The New York Times, bore a Philadelphia postmark and had no return address.

Anthrax-tainted letters were sent to numerous media outlets and offices in 2001, just weeks after the Sept. 11 attacks. Five people died, and since then, officials have been cautious when suspicious powders are detected.