Arson is suspected in a fire that destroyed most of a campaign headquarters of presidential candidate Michelle Bachelet, Chilean authorities said Tuesday.

The fire broke out about 3 a.m. in a building located in the Santiago district of Maipu and destroyed 60 percent of the structure before firefighters managed to extinguish it.

"In one sector, a bottle with fuel residue was found which could be a Molotov cocktail," Maipu fire chief Ricardo Becerra told Reporters.

The site was used to store mainly printed election materials for Bachelet, a former president who is favored to win the Nov. 17 election, and for Alberto Undurraga, a senatorial candidate for the New Majority opposition coalition.

Undurraga, the former mayor of Maipu, said that so far all available information points to arson.

"It seems to us to be unacceptable, an act of political violence that ends with a large part of the headquarters destroyed, with a large part of the advertising for Michelle Bachelet destroyed, some of my advertising also destroyed," he said.

"But beyond the material damage, it's an unacceptable act of political violence, reprehensible and it is to be hoped that the police can determine who the responsible parties are," Undurraga added.

Specialized firefighting personnel and the police are examining the evidence to determine whether the fire was intentionally set, a situation that would disrupt the calm that has prevailed to date in the Chilean election campaign. EFE