Authorities at Virginia Tech defended their decision to keep students in classes even after the gunman opened fire in a university dormitory.

It was only two hours later, after another 30 students were shot dead in an engineering building on the other side of the campus, that the sprawling university site was closed.

Charles Steger, the president of Virginia Tech, said the authorities had believed the dormitory shooting was a domestic dispute and mistakenly thought the gunman had fled the campus. “We thought the incident was contained. We had no reason to suspect any other incident was going to occur,” he said. “We can only make decisions on the information we had at the time. You don’t have hours to reflect.”

He suggested that with 14,000 people driving to the campus early in the morning, it was difficult to get the word out to everyone and that it was believed the classroom would be the safest place.

Police sources have said that there was a single gunman, firing at least two 9mm semi-automatic pistols. They have indicated that he may have been wearing a bullet-proof vest, and that he killed himself.

But in the face of a hostile press conference, neither Mr Steger, nor police chief Wendell Flinchum, would confirm that the two shooting incidents were related. Mr Flinchum told reporters they should not be “jumping to conclusions”. Asked for details about the gunman’s identity, he said: “All I can say is that he is male.”

Students complained that there were no public address announcements or other warnings after the initial shootings. They said the first word they received from the university was an e-mail more than two hours into the rampage — around the time the gunman struck again. There were unconfirmed reports that police were unable to enter the building because the door was chained.

Television showed videos taken by mobile telephones of police standing around in confusion as repeated gunshots rang out from within the engineering building.

The carnage will revive concerns over school security and access to guns that were raised last year by another spate of the school shootings that periodically afflict America.

Last night there was criticism of police and the university authorities for letting classes continue. There will also be questions about Virginia’s gun laws, which allow people to buy weapons over the counter from the age of 21.

Adam Thermos, president of the Strategic Technology Group which has designed security systems for more than 20 campuses, said: “I am so frustrated because so many academic institutions just don’t have systems in place for security — it’s always the last item on their budgets.”

President Bush said: “Schools should be places of safety and sanctuary and learning. When that sanctuary is violated, the impact is felt in every American community.”

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