The World Trade Center Responder Fatality Investigation Program, run by the state of New York, knows of more than 360 people who have died, the New York Daily News reported. The cause of death has been pinpointed in 154 cases and identified as cancer in 80.

Kitty Gelberg, a statistician tracking the deaths, said five died from suicide.

Thousands of people, most of them police officers, firefighters and laborers, dug through the remains of the Trade Center after the Sept. 11, 2001, terrorist attacks -- or through rubble that had been moved to the Fresh Kills Landfill on Staten Island. Gelberg said she will have to do a statistical comparison to determine whether the cancer rate is higher for that group than for others in their age group.

"We know people were exposed to carcinogens. There was benzene, dioxin, asbestos," said Dr. Philip Landrigan of Mount Sinai Hospital. "There's reason to be concerned, so we're engaged in watchful waiting. So far, there's no excess."