Probe of N.Y. Blast Scene Uses Videotapes, Robotics

Investigators sent a robotic probe into the gaping crater beneath the World Trade Center Monday in an attempt to determine the type of bomb that exploded there.

Meanwhile, terrorist task force members studied newly discovered videotapes that could help identify the bombers.

The robot, equipped with sensing devices and a TV camera, provided detectives with their first close-up view of the unstable and still hazardous crime scene. The measurements it took were expected to disclose with greater certainty the contents of the bomb.

Analysis of residue at the fringes of the crime scene have led experts to believe that the bomb could have included 500 to 1,500 pounds of dynamite.

“We believe it had to be a large, heavy bomb, possibly one that would test the springs of a car or van,” said James Fox, head of the FBI’s New York office.

FBI analysts will study the new videotape showing vehicles entering one entrance of the center’s underground garage, hoping to identify a heavily loaded car, van or truck.

Such a discovery “will be a major break for us,” the FBI official said.

The explosion on Friday killed at least five people and injured more than 1,000. Police said more than 40 victims remained hospitalized. Officials said they have been informed at least one and perhaps two people are still missing.

A 35-year-old maintenance worker was last seen in the basement area shortly before the bomb was detonated. On Monday, police received a report that another worker at the Trade Center was unaccounted for.

Fox said the garage also kept some records of the license numbers of arriving vehicles. While some of these are partial plate numbers, investigators will run the numbers through crime and intelligence computers.

He said his initial information was that the TV surveillance camera only recorded vehicles approaching one of the three entrances in the Trade Center’s garage. Short- and long-term public parking is allowed in the garage, which also contains the New York fleet of Secret Service vehicles and the autos of other federal agents.

Hundreds of police and FBI agents fanned out through the New York metropolitan area Monday, checking car and truck rental agencies, questioning top officials of the Port Authority of New York and New Jersey and seeking witnesses and other clues to the bombing.

Members of the terrorist task force also were examining a videotape taken by a tourist at the time of the blast. It shows people fleeing the Trade Center, and investigators will study faces in the crowd in the hope of matching them with possible suspects.

Fox said that the task force also had information about “activities of vehicles that we find quite interesting.” He said witnesses have reported that at the time of the explosion--12:18 p.m. last Friday--there were suspicious movements of vehicles near the Trade Center.

Fox declined to be more specific during a late afternoon press conference.

Underscoring the suspicion that terrorists or foreign groups may have been responsible for the blast, the Central Intelligence Agency has formed its own “small task force” to assist in the investigation.

A CIA spokesman said he was unable to identify the regional specialties of those participating in the task force.

A senior White House official said that President Clinton, who was in northern New Jersey Monday to promote his national service program, considered a visit to the bomb site, but decided against it.

“He felt at this time it would not be needed or even wise . . . until more is learned here about the situation,” said the official, who asked to remain anonymous.

The twin 110-story towers of the Trade Center remained closed Monday, but workers returned to other smaller buildings in the complex under strict security and special safety precautions.

Nevertheless, conditions near the bomb site were very unstable. An elevated causeway across West Street, which connects the Trade Center complex with the World Financial Center on the banks of the Hudson River, was closed because of newly discovered structural damage.

And bomb investigators were forced to retreat from the vicinity of the crater Monday afternoon when a wall of concrete bricks collapsed.

“It will take two or three days to shore up the garage area before we will be able to evaluate the damage and the possible cause of the explosion,” said New York’s Police Commissioner Raymond W. Kelly.

The continuing instability underscored the value of the robot probe, which resembles a big suitcase with tank treads. It carries a TV camera, a sampling arm and a sensitive listening device, law enforcement officials said.

Bomb chemists working on the edges of the crime scene have been shipping the rubble to a depot set up by police and the FBI. Experts will attempt to reassemble the crime scene and sift the debris for clues “the size of fingernails,” Fox said.

“It is a laborious, painstaking process when you go through every piece of rubble,” Kelly added.

On Monday, police met with more than 500 security officials from organizations throughout the region who gathered at police headquarters.

As the workweek began, buildings throughout New York and the nation were put on security alert. Kelly said the police had received more than 200 bomb threats since Friday afternoon--all false.

Police said they have now logged 55 calls claiming responsibility for the blast. Transcripts of these calls were being analyzed.

Fox said that experience shows that responsibility is claimed in about half of terrorist incidents. He said that after the United States retaliated a few years ago with air strikes against Libya “it sent a message that you don’t want to take credit . . . you don’t want to get caught.”

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