Two employees of the U.S. Embassy in Paris underwent medical tests Friday after handling a suspicious envelope, the embassy said.

A Paris police official said the employees were "unwell" after the incident and were examined by medical authorities at the Hotel-Dieu hospital.

The U.S. Embassy in Paris remained open Friday after two employees were sent for medical tests after a suspicious envelope was opened. (Yoan Valat/Associated Press) Chemical experts at the central laboratory of the Paris police identified the irritant as tear gas, according to a police official.

An embassy employee received a manila envelope sent as registered mail that had nothing inside, but it began emitting fumes after the employee opened it, the official said.

The official said the throats and eyes of three employees were irritated. There was no immediate explanation for the discrepancy in the number of employees reported affected.

Two months ago, Paris police were asked to investigate a similar case involving a letter to the U.S. ambassador, the Paris police official said.

The embassy could not immediately provide further information about where the latest piece of mail came from or what was suspicious about it, or the nationalities of the employees.

The mailroom is in the main building of the embassy, located just off the Champs Elysée and not far from the French presidential palace.

The embassy, which is always surrounded by layers of security, remained open after the incident, and employees were entering and exiting the building as usual Friday afternoon.

Suspicious mail has received particular attention since 2001, when five people in the United States were killed and 17 fell ill after opening letters containing anthrax.