Police in New York say a home-made device caused an explosion in Wall Street in the heart of the city's financial district.

The buildings have reopened for business and the New York Stock Exchange is operating as normal.

One man was taken to hospital with slight injuries.

"At this point it is not viewed as a terrorist act," said New York Mayor Rudolph Giuliani who was reported to have offered a $10,000 reward for catching the bomber.

The blast happened in front of Barclays Bank at 75 Wall Street in a building sublet to Dresdner Bank and J P Morgan among others.

It blew out ground-floor windows at the building. One man was taken to hospital but was released after treatment.

Police described the bomb as a home-made, simple device in a metal container like an ammunition box.

High profile

Dennis Theodore, who was working the overnight shift a street away said the explosion rocked his offices. "The windows shook. The whole building shook.

"I thought it was in my building, or right outside my building. That's how loud it was."

Joseph Muscarella, a broker at the exchange, said the area was a high-profile location for anyone wanting attention for a cause.

"It's just a shame that you have to live like this," he said.

"But it's just a part and parcel of what we do. Whenever anyone wants to protest anything, they come to the exchange."

New York City Chief of Detectives William Allee said, "We've searched the area for other devices.

"We've used bomb-sniffing dogs and we consider the area safe."

Suspect

New York City Police Lieutenant Dennis Cirillo said no-one had claimed responsibilty for the blast but they wanted to question a man who disappeared after the explosion.

He was described as a black male, wearing a tan construction coat and carrying a yellow lunch box.

The explosion did not affect subway service to the area, though some streets were closed in the morning.