Police were alerted to a man behaving suspiciously alongside the River Ouse at Lewes at 8.31am. The man is believed to have camped in the area overnight and was spotted with a large knife and other paraphenalia as he was packing.
Officers attended and were unhappy about one of the items in the man’s possession, police said.
It prompted them to seek advice from military explosive ordinance disposal experts. As a result, EOD advised that they would attend and that a cordon should be established.
A 39-year-old man of no fixed address was arrested on suspicion of making an explosive device for an unlawful purpose. He remained in custody at 11.30am today, police said.