Two Frenchmen working at the US embassy in Paris underwent medical check-ups after handling a suspect letter on Friday, but were found to be unharmed, a diplomatic spokesman said.

The two mailroom workers who handled the letter posted to the embassy were "given a clean bill of health" by medics, embassy spokesman Paul Patin told AFP. "They have been let go. They are fine," he said.

A statement from the embassy earlier confirmed that "a suspicious envelope was received" on Friday morning but embassy officials said they had no details of its contents.

"The envelope is being analysed by a laboratory. Preliminary results indicate that the envelope was not harmful," it said.

Mailrooms at US diplomatic facilities worldwide are always on the lookout for suspicious packages, amid fears that extremists might try to send in bombs or toxic materials through the post.

Patin said police were called in to the US embassy on Friday but that business there continued as normal. There was no sign of increased security at the tightly guarded site near the Champs Elysees in the heart of Paris.

The mailroom is in the main embassy building, a palace-like structure which was built in 1931 to house the first-ever US diplomatic mission, established in 1776 with Benjamin Franklin as the first envoy.