Two of the victims were occupants of a Lexus Jeep while the third was the tanker driver.
Men of the Anambra Fire Service were battling to ensure that the spilled contents of the tanker did not burst into flames.
Mr Andrew Kumapayi, Sector Commander of Federal Road Safety (FRSC) Anambra, who was at the scene of the incident, told newsmen that the head of the tanker detached from the container and fell into a deep valley beside Udoka Estate.
Kumapayi said the wounded had been rushed to Chukwuemeka Odumegwu Ojukwu University Teaching Hospital (COOUTH) for treatment by FRSC rescue team who arrived almost immediately.
He said the vehicles involved were the petrol tanker and a Lexus jeep all on the Enugu bound lane of the Enugu-Onitsha Expressway.
The sector commander blamed the incident on over speeding.
Kumapayi, who expressed worry over the attitude of heavy-duty truck drivers, warned motorists to exercise utmost care on the road in the interest of all.