This b/w photo released by the Royal Pigeon Racing Association, shows the skeletal remains of a pigeon discovered in the chimney of a house in southern England which carried a mysterious, long-forgotten message from World War II. Historians at Britain’s Second World War-era code breaking headquarters at Bletchley Park say the bird was almost certainly returning from Nazi-occupied France during the June 1944 D-Day invasion. Bletchley Park says that a radio blackout imposed on Allied forces at the time meant that messages about the progress of the invasion were dispatched by pigeon across the Channel. What the message says remains unknown. It was coded, an unusual measure generally reserved for the most sensitive secrets. Bletchley Park said Thursday that one of its curators is now trying to unravel the message using World War II logbooks. (AP Photo / Royal Pigeon Racing Association ) (AP/AP)

A World War II code found strapped to the leg of a dead pigeon stuck in a chimney for the past 70 years may never be broken, a British intelligence agency said Friday.

The bird was found by a man in Surrey, southern England, while he was cleaning out a disused fireplace at his home this month.

The message, a series of 27 groups of five letters each, was inside a red canister attached to the pigeon’s leg bone and has stumped code breakers from Government Communications Headquarters, Britain’s main electronic intelligence-gathering agency.

“Without access to the relevant code books and details of any additional encryption used, it will remain impossible to decrypt,” an agency spokesman said.

The message is consistent with the use of code books to translate messages which were then encrypted, according to GCHQ, one of Britain’s three intelligence agencies.

However, without knowing who the sender, “Sjt W Stot,” is or the intended destination, given as “X02,” it is extremely difficult to decipher the code, the agency said.

Although the code books and encryption systems used should have been destroyed, there is a small chance that one exists somewhere.

An agency spokesman said it was “disappointing” that the message brought back by a “brave” carrier pigeon cannot be read.

The Curator of the Pigeon Museum at Bletchley Park, north of London, Britain’s main code-breaking center during World War II, is also trying to trace the identity numbers of the pigeon found in the message, according to GCHQ.

Pigeons were used extensively in the war to carry vital information to Britain from mainland Europe. Flying at speeds of up to 50 mph, they can travel distances of up to 620 miles . But they are vulnerable to hungry hawks; during the war, bored soldiers used to take potshots at them.