General Adel Rafat, head of security in the Suez city region, said the explosives were found in a truck entering the al-Shahid Ahmed Hamdi tunnel that links the mainland to the Sinai peninsula, dailynewsegypt.com said Sunday.
Local media reports said the explosives were destined for the Gaza Strip.
Rafat said the truck driver was detained by police and will be presented before the city's prosecutor. He said the passengers in the truck are suspected of planning to carry out an ambush in the tunnel, but did not say how many they were and if they were arrested.
He said in the past ten days, police seized a total of 2.5 tons of explosives in three instances.
Also Sunday, Israel Radio said Egyptian security forces arrested 10 Palestinians who crossed into Egypt via smuggling tunnels in Gaza.