The agency that owned the World Trade Center was liable for the fatal 1993 bombing by terrorists in the complex’s underground parking garage, an appeals court said yesterday.

A five-judge panel of the state Supreme Court unanimously agreed with a lower court judge who had refused to set aside a jury verdict that the Port Authority of New York and New Jersey was negligent and more than 50% liable.

The Manhattan jury found in 2005 that the agency had not properly protected its underground public parking garage, where terrorists blew up a rental van loaded with explosives on February 26, 1993.

The blast killed six people and injured almost 1,000 others. It also blew out a crater about six stories deep that covered an area the size of a football field under the building complex, the appellate judges said.

The appeals court noted the Port Authority did not argue that the bombing was unforeseeable, since the bombing method was not only foreseen but was brought to PA executives’ attention by the agency’s own internal study group.

The group’s report said the trade center was vulnerable to terrorist attack through its parking garage. It detailed “with exact prescience” how that vulnerability could be exploited, the appeals court said.

“Here, the evidence overwhelmingly supported the view that the conscientious performance of defendant’s (PA’s) duty reasonably to secure its premises would have prevented the harm,” the appeals judges wrote.

Lawyer David Dean, who argued the case against the PA in the lower court in 2005, said he was “ecstatic” and “overjoyed” by the appeals court ruling.

Mr. Dean said the “thoughtful, strong and well-written” ruling “surprised me with the intensity of its criticism of the Port Authority. It says they could have prevented the bombing, but they rejected their own report.”