A power failure hit 40 percent of Venezuela on Tuesday, including much of Caracas, according to an Associated Press report..

The blackout was caused by a forest fire that overheated power lines in the central state of Guarico, the energy ministry said in a statement.

Power returned to downtown Caracas after about an hour and a half, then went out again and soon returned. Officials said power also was being re-established in other parts of the country.

The blackout caused stoplights to stop functioning, aggravating traffic jams, and temporarily closed some subway stations in Caracas. Workers emerged from darkened buildings, the AP story said.

The transmission lines that overheated and failed were near the Guri hydroelectric dam in eastern Venezuela, said Gen. Hipolito Izquierdo, president of the National Electric Corp.

He told state television that the initial failure set off a chain reaction during peak power consumption hours on a hot day.