Empty stretcher reminds New York of its lost victims

The trauma of 11 September was revisited in New York yesterday as hundreds gathered in Manhattan to mark the formal ending of the recovery and clean-up effort at ground zero.

The trauma of 11 September was revisited in New York yesterday as hundreds gathered in Manhattan to mark the formal ending of the recovery and clean-up effort at ground zero.

The brief ceremony began as fire and police workers bore an empty stretcher up a long metal ramp out of the pit where the twin towers once stood, to symbolise the 1,700 victims whose bodies have not been found or identified. The stretcher was followed by the last steel column left standing until it was felled two days ago.

The closing of the clean-up chapter at ground zero came as the country continued to search for new ways to thwart terror attacks. Officials have warned that al-Qa'ida or other groups could return with smuggled weapons that may include "dirty bombs" designed to poison populations with biological substances or, indeed, nuclear bombs.

By the end of the year all customs officers will be equipped with pocket-sized scanners which can detect tiny amounts of radiation. About half the officers at some 300 points of entry, at airports, cargo terminals and land-crossings, already have the detectors.

Robert Bonner, the US Customs chief, said he believed al-Qa'ida was "determined to strike the United States again". He added: "We don't know if al-Qa'ida or related terrorist organisations have a nuclear device. What we do know is that for at least the last five or more years they've attempted to get radiological materials to build a nuclear device. They consulted with a Pakistani scientist or engineer who was involved in the Pakistani nuclear development. Certainly there's been an attempt to get a device. The question is, 'Should we be concerned about it?' This is one of those areas where I don't want to wait and see what happens."

At the same time, the customs service is seeking to reach agreements with governments around the world, including those of France, Germany and the Netherlands, to allow its agents to inspect cargo ships bound for the US before they leave port.

Providing a model of future bilateral agreements, the US already has customs officers inspecting ships in Canada before they leave for American ports.

Mr Bonner said: "I have proposed that we essentially move our zone of security outwards, that we have a strategy for searching and inspecting containers that are high risk, for example, at the point of origin rather than the point of arrival – rather than waiting for the container to come in to the Port of Baltimore."

Even within the US, extraordinary steps are being taken to identify possible terrorists, none more startling than at the Statue of Liberty in New York. Discreetly placed cameras now capture the images of tourists as they board boats for the trip to Liberty Island. While the boats make the crossing, agents compare the faces with a database of people previously identified as belonging to terrorist groups.