By Gul Yusufzai

QUETTA, Pakistan (Reuters) - Pakistani firefighters were battling on Wednesday to douse a fire still raging more than a day after a series of explosions on a decommissioned oil tanker, with the death toll rising to 17, and more than 20 workers missing, officials said.

Tuesday's initial blast occurred as workers were welding near a fuel tank in a shipbreaking yard in Gaddani, 45 km (28 miles) northwest of the southern port city of Karachi, said Zulfiqar Bokhari, a local administration official.

"The fire is still burning," said Bokhari, adding that civilian and military firefighters were struggling to put out the flames, which had been ignited by two blasts in quick succession and followed by eight more explosions.

At least 58 people were injured in the blasts, and between

20 and 25 people were still missing, he added.

Laborers in Gaddani often work in poor conditions without basic protective gear.

The Gaddani ship-breaking industry, which has fallen on hard times recently, employs about 9,000 workers, far fewer than during its boom years at the end of the last decade.

(Writing by Asad Hashim; Editing by Clarence Fernandez)