NEW YORK – Authorities have warned people about a huge emergency-response drill set for New York City's World Trade Center on Sunday, seeking to avoid panic like one caused by an unannounced flyover by a U.S. presidential plane.

More than 800 emergency responders -- mostly police and firefighters -- will practice responding to a simulated explosion on a commuter train in the tunnel below the Hudson River that separates New York from New Jersey.

The drill is set to run from 6 a.m. to 11:30 a.m. (1000 to 1530 GMT) at the transit hub, which is surrounded by construction sites for skyscrapers and a memorial for victims of the September 11, 2001 attacks.

People will see and hear lots of sirens and lots of emergency response, said Steve Coleman, a spokesman for the Port Authority of New York and New Jersey, which owns the World Trade Center site and operates the trans-Hudson commuter line.

The World Trade Center site has been attacked twice, first by a truck bomb in 1993 and then in the September 11 attacks that destroyed the Twin Towers in 2001.

Since then, Madrid, London and Mumbai have been hit by attacks on their transit systems, putting New York on alert.

On April 27, a plane used by President Barack Obama, trailed by a fighter jet, flew low over the Statue of Liberty near the World Trade Center site, creating a panic among New Yorkers who lived through September 11.

But it turned out the flight, which was not announced to the public, had been staged for a photo shoot.

The aide who authorized the flyover resigned on May 8, saying the controversy made it impossible for him to lead the White House Military Office.

Coleman said the warnings issued ahead of Sunday's event were not necessarily related to that snafu.

We have done similar drills with similar types of warnings. Obviously this is bigger-scale drill so we are doing a little bit more. I don't think it's strictly because of what happened two weeks ago with the flyover, Coleman said.