Two American tourists were found sleeping off a heavy night at the heights of Paris' Eiffel Tower on Monday, after dodging security the night before, the monument's operator said Tuesday.

Security guards roused the men "in the early morning" as they were making their rounds before the French landmark's 9:00 am opening time, publicly-owned Eiffel Tower operator Sete said.

They "appear to have got stuck because of how drunk they were," Paris prosecutors told AFP.

The inebriated Americans had spent their illicit night under the stars in a spot normally closed to the public between the tower's second and third levels, but "did not pose any apparent threat," said Sete.

After paying for an entry ticket around 10:40 pm on Sunday, the pair hopped security barriers while climbing down the stairs from the tower's top, a police source said.

Firefighters, including a specialist unit for recovering people from dangerous heights, were sent to recover the interlopers, the police source added.

Both men were brought to the police station in Paris' seventh district for questioning, while Sete said it would file a criminal complaint.

The discovery of the nocturnal infiltrators delayed the tower's opening to the public on Monday morning for around an hour.

Two bomb threats on Saturday forced the evacuation of the landmark, and police are now investigating.

A further email with a bomb threat against the 330-metre (1080 feet) steel tower was sent to three Paris police stations on Monday, but police advised against evacuating it.