* Non-unionized workers want strike lifted
* Main union wants vote discarded, says not legal
* Strike over pay, working conditions (Adds comment from Drummond workers)
By Luis Jaime Acosta and Helen Murphy
BOGOTA, Sept 6 (Reuters) - A vote to end a more than six-week-long strike by union employees at U.S. coal miner Drummond's Colombian operations does not end the work stoppage until the labor ministry makes a definitive ruling, official and worker sources said on Friday.
The decision to lift the strike now rests with the ministry, which will study the arguments from minority unions that want to return to work and the majority union, which wants the strike to continue, a labor ministry source told Reuters.
Sintramienergetica, the mining and energy sector union that instigated the walkout, might be obliged to stop the action and return to work, he said. The ministry has not yet received the paperwork soliciting the end to the strike.
The ballot, which took place on Thursday, had support from unions representing a minority of Drummond's direct employees.
Even so, with slightly more than half of Drummond's 5,000 direct employees voting on Thursday in favor of ending the work stoppage, pressure will mount on Sintramienergetica to end the strike unilaterally, another industry source said.
Sintramienergetica Vice President Edgar Munoz told Reuters the union was not yet ready to call a halt, and was to consult with workers and the Labor Ministry. He also said the voting might have been tainted by fraud.
"We have not contemplated lifting the strike, not under the conditions that the company wants," Munoz said. "The vote was not legal, and we will ask that it not be recognized."
Workers at Drummond, Colombia's second-largest coal miner, have been on strike since July 23 over pay, work conditions and a demand that 400 port workers be given other jobs when automated loading is introduced next January.
The strike has shut down Drummond's two mines and private port and cut the country's coal output by about a third, putting a drag on economic growth in the country's largest mining sector. It has had little impact on an amply supplied global coal market.
Drummond workers said on Friday that they want to return to work. A spokeswoman, who asked not to be identified, said paperwork has been sent to the labor ministry calling for the strike to be lifted and for any outstanding problems to be resolved through arbitration.
The price of European physical coal for November delivery dropped on Friday to $75.60 per tonne, down $1.70 from the previous session.
Sintramienergetica says it represents about 2,900 of Drummond's direct employees in Colombia, the world's fourth-largest coal exporter. Drummond also employs roughly the same number of third-party contractors who cannot vote.
The vote and subsequent confusion when some local media interpreted it to mean the end of the strike, is likely to put more pressure on Sintramienergetica, which for now is allowing the strike to continue. The fact that a majority of direct employees voted in favor of going back to work also implies that some of the union's own membership voted to end the strike.
In all, 2,549 of the direct employees, slightly more than half the workers, voted to end the strike, Drummond said.
While reiterating that the strike will continue, Munoz expressed some uncertainty about its duration.
"Will the strike be lifted?" he asked. "That's the million-dollar question." (Additional reporting and writing by Peter Murphy.; Editing by Gerald E. McCormick, Lisa Von Ahn, Gunna Dickson and Andre Grenon)