Radiation fear spreads panic through US

· Broadcast 'rings of fatality' diagrams heighten fear
· Radioactive material on 2m licensed sites

The news of the possibility of a "dirty bomb" attack on the US sent fresh waves of concern across the country, with listeners calling talk shows and television news programmes to ask what medicines they should stock up on, and what the chance of surviving such an attack would be. Shares on Wall Street slipped in response to the news.

There was little comfort to be found in the announcement by the nuclear regulatory commission yesterday that no fewer than two million locations in America are licensed to have radioactive materials, and that annually about 300 pieces of radioactive material go missing. There have been 1,500 such disappearances in the past five years, according to the NRC.

The so-called dirty bomb would not result in a nuclear explosion, but could release radiation over several city blocks.

Weapons experts said a dirty bomb was well within the technical capacity of al-Qaida. The main difficulty would be in acquiring radioactive material, but it could be stolen from nuclear waste depots or hospitals, where it is used in medical equipment.

Such a bomb could cause radiation sickness among people caught in the immediate vicinity of a blast, and cancer among those further afield who inhale radioactive particles. But its most devastating effect would be to make a large area of a city uninhabitable.

People in the US have become accustomed over the last few weeks to receiving warnings of terror attacks of one kind or another. But the new suggestion of radiation bombs is likely to revive concerns, not least because it has been receiving widespread tele vision coverage, complete with diagrams showing rings of danger from fatality through the penetration of gamma rays and the fact that there are no treatments to halt the process.

The government made early efforts to reassure the public. "We have no information that suggests this [plot] advanced beyond planning stages," the White House spokesman, Ari Fleischer, said yesterday. The deputy defence secretary, Paul Wolfowitz, said there was no certainty that Washington was the initial target.

Not least among the concerns being expressed is the fact that the man accused of conspiring with al-Qaida to construct and place the dirty' bomb hardly fits the profile of a would-be Islamic fundamentalist bomber

Born Jose Padilla in New York 31 years ago into a Puerto Rican family, Abdullah al-Muhajir was in trouble with the authorities as a teenager, having moved with his family to Chicago when he was about five. His father is said to have died while he was young and his mother now lives in Florida.

At the age of 15, while still called Padilla, he was arrested for aggravated battery, armed robbery and attempted armed robbery and jailed. He was by then already a member of a Chicago street gang.

But unlike many other converts who found religion in jail, he is said to have been converted when he fell in love and married a Muslim woman who encouraged him to become a Muslim.

He continued to have problems with the law after his release from prison and when he was detained last month there was still an outstanding warrant for his arrest dating back to 1997. He had also attacked a sheriff's deputy following a traffic dispute, according to reports.

He spent a year in jail awaiting trial after a .38 revolver was found at his house. He was convicted, but was released because of the time he had already spent inside.

But a neighbour in the Latino area where he lived in Chicago yesterday described him as "a very sweet person".