Warsaw: The unexpected explosion came as a result of an attempt to defuse a World War II-era bomb found underwater in Poland.
In 1945, a dolphin bomb used by the British Royal Air Force during World War II was found in the Beast Canal.
Residents were evacuated to a safe place to defuse the 5400 kg bomb.
The bomb exploded unexpectedly underwater during a subsequent Coast Guard bomb disposal operation.
However, no one was reported harmed.
"There was an explosion during the deactivation operation. No need to worry any more about the bomb. No one was hurt. " Navy officials said.