NEW YORK (AP) _ The gas-like odor that hung over Manhattan's streets was gone Tuesday, but city officials were still trying to pinpoint its source _ and eyeing New Jersey.

Charles Sturcken, a spokesman for the city Department of Environmental Protection, said Tuesday that his agency was pretty sure the source of the smell was along New Jersey's industrialized waterfront, just across the Hudson River from New York.

"The way we tracked the dispersion of the smell and the prevailing winds indicates that it came from New Jersey, somewhere near Secaucus," Sturcken said.

The strong odor, detectable from Manhattan's southern tip to well past Central Park, led to some precautionary evacuations, and about a dozen people were taken to hospitals complaining of difficulty breathing, Fire Department spokesman Tony Sclafani.

There was no indication that the air was unsafe, though, and no indication of terrorism, city and federal officials said.

"It may just be an unpleasant smell," Mayor Michael Bloomberg said at a midmorning news conference Monday.

Complaints about the odor also came from Bergen and Hudson counties in New Jersey, but no air sampling was done there because the state Department of Environmental Protection had no specific locations to test, spokeswoman Elaine Makatura said.

Sturcken said that the odor could have been caused by mercaptan, the chemical added to normally odorless natural gas to make it easily detectable, but he added, "Nothing has been confirmed."

"We're left with a mystery, although we know it's not harmful," he said.