Clay Tiles are the Source Behind Radioactive Cargo

A tense three-day hunt for deadly radioactive material on a cargo ship bound for New Jersey. Government scientists determined the radiation came from a harmless container of clay tiles. Traces of radiation are not uncommon in any number of natural materials such as clay, cement, dirt or plants.

The Department of Energy dispatched teams of nuclear scientists. The Coast Guard ordered the ship to remain offshore. The FBI took a lead role in the inquiry and anti-terrorism officials received regular briefings. President Bush also was briefed, one source said.

Bush's presence in New York for Sept. 11 ceremonies and his speech to the United Nations General Assembly also loomed large in the decision to keep the ship miles away from the coastline. Finding the source of the radiation with the ship out at sea was a nightmare. Hundreds of containers were stacked one on top of the other in the ship's huge cargo holds, officials said. With no dock to unload on, the nuclear team struggled to identify the radiation source. The search then had to postpone because of high winds and rough seas.

The Pentagon dispatched its own team to the ship. Lt. Col. Rivers Johnson, a spokesman, acknowledged that units with "unique capabilities" were sent to the vessel. But by that time, the Energy Department scientists had identified the source: a single container of clay tiles.

The decade-old freighter could spend several days unloading its cargo in Elizabeth. From there, its next port of call is Norfolk, Va.

"If you know what you are doing, you can make (nuclear materials) very difficult to detect," said Charles Gentile, an engineer from the Princeton Plasma Physics Laboratory who is developing a new sensor for homeland security. Detection is made harder by the fact that lots of objects-- from cement to bananas-- naturally emit low levels of radiation.

"I'm radioactive and you're radioactive," said Arden Dougan, a nuclear chemist at Lawrence Livermore National Laboratory who is studying ways to detect radiation in cargo containers. "It's a natural part of living."