Scientists have found new evidence suggesting a giant tsunami that crashed in New York City 2,300 years ago, was caused by an asteroid 330 feet in diameter, which slammed into the Atlantic Ocean nearby.

According to a report in Discovery News, Katherine Cagen of Harvard University and a team of researchers found clues in the form of slit in the Hudson River, which indicates an asteroid impact in the past.

While sifting through samples, the researchers found carbon spherules, which are perfectly round particles that form in the extreme pressures of an impact.

"But the main thing that closes the deal is that we looked in the spherules and found nano-diamonds," said Dallas Abbott of Columbia University, a co-author on the work. "These have only been found in impact ejecta or in meteorites," he added.

The team found grains of several shocked minerals in the sediments as well.

So far, the team has only found impact ejecta in deposits in the Hudson, with some as far as 50 kilometers (31 miles) upriver from the mouth. But, they have taken samples of suspicious-looking sediments along the coasts of New Jersey and Long Island as well, and hope to find more of the same strange minerals pointing to an impact origin.

"We've had strong storms in New York's history that haven't made deposits anything like this," Cagen said. "We don't know how big it was, but it would have been more than a splash against Manhattan; the city would have been devastated," she added.

Cagen is convinced her team's work proves an impact caused the tsunami, but admits they'll need to find the smoking gun - a crater, probably buried in the continental shelf off New Jersey - to convince skeptics.

"We're making the pretty outrageous claim that not only did a tsunami hit the New York metropolitan area 2,300 years ago, but it was caused by an asteroid impact for which we can't find a crater," she said.