More workers joined a strike at BHP’s Port Hedland operations in Western Australia on Sunday, a union spokesperson said, in the first major industrial action at the ‌iron ore export hub in a quarter-century.

On the second of the planned two days of stoppage, some 100 workers downed tools at the world’s biggest export hub for iron ore at 5:30 a.m. (21:30 GMT), taking the total involved to around 150, the spokesperson said.

Sunday’s 24-hour stoppage by the three unions of the Combined BHP Ports Unions, which represents some of BHP’s ‌workforce of more than 800 people ⁠at the port, followed a 24-hour ship-loading halt on Saturday.

Melbourne-based BHP, which ships some $80 million worth of iron ore daily through the port, said vessels continued to be loaded on Sunday amid the strike.

After workers return to their jobs from 5:30 a.m. on Monday, the next step, the CBPU spokesperson said, will be to resume negotiations on August 18, seeking a four-year bargaining agreement with BHP, the world’s third-largest iron ore miner.

The union went ahead with the strike, the first of its kind since 2000, despite progress in talks between the parties on Tuesday.

The action is not expected to affect rival miners Fortescue and Hancock Prospecting, which also ​use Port Hedland. The hub accounted for 75% of iron ore ​exports from ⁠the Pilbara region of Western Australia in the year to June.

(By Sam McKeith; Editing by William Mallard)