A senior security official in Algeria has said that a big explosion last month was caused by a car bomb.
At first authorities said the blast was probably caused by a technical fault
The explosion, on 21 June, injured 11 people and damaged the main electricity plant in the capital Algiers.
Algeria's main Islamic group, the GSPC, said it carried out the attack, but until now officials had suggested that the blast was due to a technical fault.
The bombing suggests Algeria's Islamic militants want to show they can still attack at the heart of the state.
The Salafist Group for Preaching and Combat (GSPC) said at the time that the attack proved the authorities did not have control of security in the capital.
And now, admitting it was a car bomb, Algeria's police chief Ali Tounsi has said more than 500 extra police officers will be deployed in Algiers to reinforce security.
In the mid 1990s - at the height of the civil war - bomb attacks by Islamic militants in Algeria were commonplace.
But in recent years security has greatly improved.
By attacking a major energy installation in the capital, Algeria's Islamist militants hope to shake public confidence and scare away the investors the government so keenly wants.