Washington  - High profile Harvard Law School professor Alan Dershowitz received an envelope laden with white powder, after a number of similar letters were sent to a New York newspaper earlier this week, the Federal Bureau of Investigation said Thursday.

All the letters were postmarked from Knoxville, Tennessee, the FBI said in an e-mailed statement. The case is being handled by the Knoxville FBI Joint Terrorism Task Force.

At The Wall Street Journal, the discovery prompted the evacuation Wednesday of one floor used by both executives and editorial page staff, and all Journal employees were sent an email warning them not to open any post.

White powder mailings trigger huge alarms in the United States after the 2001 anthrax attacks delivered via mail to media outlets and members of Congress in September and October 2001.

Five people were killed and dozens others were injured, spreading alarm in the fearful atmosphere just after the September 11, 2001 terrorist attacks.

The Wall Street Journal said at least 10 envelopes were held in the building's mail room, but three had already been distributed.

New York City Police Department's Emergency Services Unit and the FBI responded to the scene Wednesday and were testing the letters to determine whether they contained a hazardous substance.

Dershowitz is a high profile criminal defence lawyer who has handled cases for OJ Simpson, Patricia Hearst, Mike Tyson and Claus von Buelow.

He is also a well known commentator on Middle East and press freedom issues. It was not clear if he had opened the envelope or was at risk in any way.

"Right now our first priority is the safety of our citizens," said Richard Lambert, the special agent in charge of the Knoxville FBI. "We take these matters seriously and will investigate all leads to determine who sent the letters and why." (dpa)