Police have now issued a health warning after it emerged that the blocks may be treated with an arsenic-based preservative.
The materials were taken last week from the Dover Western Heights Tunnels which are owned by English Heritage.
Police in Dover are appealing for witnesses or any information that may help their investigation into the theft of English Heritage owned wooden floor blocks.
The construction of Western Heights began during the Napoleonic wars and was completed in the 1860s to protect Dover from a French invasion.
Dover Community Safety Inspector Guy Thompson from Kent Police, said: `This is a heritage crime where these blocks are more than one hundred years old.
“It would have taken several trips to remove so many blocks so we’re appealing to anyone who may have seen suspicious behaviour in the area of Military Road over a period of time.
“Our main concern at the moment is to alert those who may come into contact with the flooring, that they could be a health hazard, especially if burned as fuel.
“Dealers, home renovators, collectors and the suspects themselves need to be aware of the potential danger.”
Two suspects were seen on 27 February at 11am and one of them was a woman. She is described as in her 20s, about 5ft 2ins tall, medium build with black hair and a blue top. She was carrying a large rucksack.
