Updated at 9 a.m. Tuesday

A dead body in a car - and a note warning people not to come near - kept neighbors guessing and a street barricaded for hours Monday as emergency vehicles and personnel in white hazmat suits converged on a spot in Pennsbury Township, Chester County.

Police said Tuesday they found potentially toxic chemicals in the car after a more than six-hour operation during which the body of a 30-year-old Kennett Square man was removd from the vehicle. They did not identify the chemicals further.

Patty Mains, a spokeswoman for Chester County's Department of Emergency Services, said a 911 call about 12:30 p.m. suggested that a man had committed "chemical suicide" inside the car was on East Hillendale Road at Virginia Place.

Neighbors said the car apparently veered down a gravel path into a nearby field. A neighbor who was walking his dog made the discovery - and saw a written message that warned him not to open the car door, he said.

From behind orange tape, neighbors watched wide-eyed for hours Monday as emergency crews, including officials from the coroner's office, scurried in and out of a makeshift command center.

Only members of the hazardous materials team, clad in protective white suits, approached the car, which could not be seen from outside the cordoned-off area.

At one point, the men in protective gear - who were hosed off after visiting the car - dragged what looked like an industrial fan toward it. Minutes later, emergency crews suddenly ran from their command post, ducking under the barrier separating them from spectators.

A second later, spectators followed suit as a whoosh of air that smelled like sulfur wafted through the crowd of about 30 people.

"I sure hope it's not toxic," one man said as he retreated.

Raymond Heller, who has lived nearby since 1985, said he first realized something was amiss when he looked up from painting his deck to see a TV helicopter hovering overhead.

He and his wife, Suzanne, said they saw several ambulances, which arrived without sirens. Fire trucks and emergency vehicles followed, including one for the hazmat team, they said.

Cheryl Whiteley, who moved to the neighborhood two years ago, said it usually is quiet.

"This is the most activity I've ever seen here," she said. "I just wish they would tell us what's going on."

Contact staff writer Kathleen Brady Shea at 610-696-3815 or kbrady@phillynews.com.