A chemical that sickened two workers Sunday at a Kennedy Airport postal facility turned out to be nail-polish remover, according to a source close to the investigation.

It was not known how the two customs workers were exposed to the product.

No other workers were treated.

Earlier Sunday, the postal facility was sealed off and employees were ordered to leave their vehicles in the parking lot.

Workers were shuttled home by bus and there was no further information available about when they could retrieve their vehicles or get a bus ride to work Monday, officials said.

FBI officials sent agents to the scene to test the customs workers for exposure to hazardous or potentially deadly gas "out of an overabundance of caution."

The FBI testing followed some initial tests that indicated a possible cause for concern, FBI officials said.

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The employees were opening mail in the airport post office when they were sickened by the contents of a package, Port Authority officials said.

The package was part of a shipment from China, the officials said.

After they were checked for chemical exposure, the two employees were taken to Franklin Hospital Medical Center in Valley Stream for treatment, a New York City Fire Department spokesman said.

Their conditions were not known late Sunday afternoon.

Port Authority officials said the opened package was sealed in a 55-gallon drum.

The roads near the postal facility were reopened at about 6 p.m. Sunday.

Sunday afternoon, the roads leading to Building 250, near Cargo Area D, were closed.

Workers could be seen leaving the postal facility for the day and waiting for a bus that would take them home.

Several employees said they were taking the latest scare in stride. The busy postal facility handles packages and envelopes from around the world every day.

Workers have dealt tightened security and similar chemical scares in the past, employees said.

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And with several bomb scares high-level security threats under their belts, the workers at the Kennedy Airport mail facility are veterans of the unexpected, said Roshon Martin, 42, of Jamaica, a supervisor at the facility.

"They always take care of you," Martin said of investigators.

With Anthony Destefano and David Schwartz and the Associated Press