No one was hurt when a homemade bomb exploded here early Friday outside an office of Mexico's CFE electric utility, the state-owned company said.

The blast occurred shortly after midnight Thursday near the door of a customer service office in the capital borough of Iztacalco, the CFE said in a statement.

The explosion damaged the office's facade and entrance hall, according to the statement, which said authorities are investigating the incident.

Anarchist and anti-globalization groups and radical environmentalists are known to set off makeshift explosive devices outside shops, bank branches and automatic teller machines in Mexico City.

The attacks almost always take place in the middle of the night and rarely result in injuries or arrests.

No casualties were reported after a bombing last week outside a shuttered nightspot in the capital's Lomas de Chapultepec neighborhood.