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CLEVELAND (AP) _ A Continental Airlines flight with 155 people on board was quarantined at Cleveland Hopkins International Airport on Monday because of concerns that there may be anthrax aboard.

The U.S. Environmental Protection Agency conducted a field test on the substance, which was discovered in the airplane's bathroom, and concluded it was not anthrax.

The test showed no indication the substance posed any threat, and passengers were able to leave the plane after a delay of about four hours.

The EPA will conduct additional tests to determine the nature of the substance.

Continental Airlines flight 456 from Las Vegas to Cleveland was quarantined after a flight attendant discovered the white powder in the plane's bathroom and notified the captain.

The FBI, police and a hazardous materials team were dispatched to the scene and the plane was taken to ``a secure section of the airport,'' according to Mayor Michael R. White's press office.