A man carrying a hoax bomb triggered an evacuation of the main terminal at New York's LaGuardia Airport Saturday, delaying thousands of travellers, authorities said.

Multitudes were forced onto pathways and roadways around the complex, tying up incoming traffic for hours, officials said.

Scott McGann, 32, of New York, was arrested on charges related to "placing a false bomb" in a transportation facility and "making terroristic threats," said John Kelly, a spokesman for the Port Authority of New York and New Jersey.

Authorities were first alerted by a United Airlines ticket agent shortly after 5.00 am local time when Mr McGann arrived, Mr Kelly said.

After issuing Mr McGann a boarding pass the agent telephoned Transportation Security Administration officers he was en route to a concourse checkpoint.

Security officers were tipped off by a second caller about "a suspicious male" who was "possibly intoxicated" heading for security screeners, Mr Kelly said.

"He did not respond to questions and was acting very suspiciously, suspicious enough that our officers felt it warranted police action," Mr Kelly said.

Police then removed a duffel bag stuffed with wires and batteries.

"The bag was suspicious enough that it warranted evacuation of the terminal building," Mr Kelly said.

A Federal Aviation Administration spokesman said even the control tower was evacuated except for two air traffic controllers who remained on duty to handle aircraft landings.

A spokesman for the New York Police Department said its bomb squad was dispatched to the airport.

The team suited up in protective gear and x-rayed the bag, the spokesman said.

Members of the bomb squad "contained the device" but eventually determined it was "a hoax device, inert," the spokesman said.

Dwayne Baird, a Transport Security Administration spokesman, said the terminal was "swept and later cleared" for reopening, a few hours later.

By then those in the terminal and those arriving had filled airport roadways disrupting traffic, causing delays lasting into the day. An FAA spokesman said there was no way to immediately determine the number of people or flights delayed.