ANTOFAGASTA, Chile (Reuters) - A fire in the workers' barracks of BHP Billiton's (>> BHP Billiton Limited) (>> BHP Billiton plc) Escondida copper mine in Chile, the world's largest, left three workers injured early Friday, the company said.

The fire, which affected three employees of companies that provide third-party services to BHP, occurred as the mine's largest union enters the second day of a strike that has stopped production at the massive deposit.

The company, which is continuing some limited operations during the strike, such as new construction, said the causes of the fire where under investigation.

"In the early morning hours, for reasons that are being investigated, a fire occurred in Unit 30 of Camp 7,000," BHP told Reuters in a statement.

It added that the injuries of the three workers, who were involved in the expansion of its Los Colorados concentrator, were not life-threatening.

The striking workers in the 2,500-member Escondida Union No. 1, who are currently camped outside the mine complex where the fire occurred, said they had no additional information on the incident, but said the barrack in question had not been occupied for some time.

"We don't have access. We don't know the extent of what happened," said Carlos Allendes, the union spokesman.

Escondida is majority-controlled by BHP, with Rio Tinto (>> Rio Tinto Limited) (>> Rio Tinto plc) and Japan's JECO (>> JECO CO., LTD.) also holding stakes.

Copper prices have soared in recent weeks amid fears of a supply disruption at Escondida, which produced 6 percent of the world's copper in 2015. The metal was trading at $5,941 per tonne at 10:32 a.m. local time (1332 GMT), near one-and-a-half-year highs.

(Reporting by Fabian Cambero; Writing by Gram Slattery; Editing by Phil Berlowitz)

By Fabian Cambero