Dunstable warehouse filled with fly-tipped waste
Fly-tippers filled an empty warehouse with rubbish after cutting a lorry-sized hole in the wall.
The Environment Agency found the household and commercial waste illegally dumped inside the warehouse in Dunstable, Bedfordshire.
Tracy Nash, of the Environment Agency, said: "This callous act has endangered the environment and had a costly impact for the land owner."
The agency is appealing for information about the dumping of the waste.
About 3,000 cubic metres (106,000 cubic ft) of waste was dumped at the former Ecomold site in Luton Road.
"This is not a matter of small scale fly-tipping. This case appears to be intentional large-scale avoidance of disposal costs," said Ms Nash.
"It is vital that we identify where the waste came from and who transferred it to the warehouse.
"If an innocent party has handed it to a contractor for disposal in good faith then they won't be in any trouble and may have critical information for us."
The waste was dumped between 16 and 20 November but was not discovered until January.
Work to remove it is due to begin shortly at the landowner's expense.
The Environment Agency said those responsible for running illegal waste sites could be fined up to £50,000 in magistrates' court and face unlimited fines in higher courts, as well as community punishment orders or prison sentences of up to five years.