Plane
The 29-year-old man, from Pennsylvania, was taken into custody at Philadelphia International Airport while attempting to board a plane for San Francisco. (Reuters)

A man is in custody in the United States after he attempted to board a plane in Philadelphia with explosives in his backpack, CBS reported.

The incident is not thought to be terrorist-related, sources said.

The 29-year-old man, from Pennsylvania, was taken into custody at Philadelphia International Airport while attempting to board a plane for San Francisco.

He had three M-80 type fireworks and some explosive powder in his backpack, which he said he had forgotten about.

The incident caused a gate at the airport to be temporarily closed while the bomb squad was called to remove the material for examination.

The FBI is questioning the man.