* Protest over factory safety lasted some 12 hours
* Workers to meet with officials, companies on Tuesday (Recasts with normal activity resuming)
BUENOS AIRES, Dec 6 (Reuters) - Soy-crushing workers in key Argentine grain ports started to resume normal duties on Monday following a brief protest over safety conditions that brought plants to a virtual halt, a union leader said.
The protest, which started at midnight (0300 GMT), affected soy-crushing plants and ports in Puerto San Martin and San Lorenzo, although workers agreed to undertake some maintenance tasks.
"Normal activities have resumed," Hugo Lopez, a leader of the San Lorenzo soy-crushing workers' union, told Reuters. "Tomorrow there'll be a meeting with the Labor Ministry ... and then we expect serious negotiations to start."
Workers were protesting over safety conditions for contractors in crushing plants following a fatal accident last week at a factory in the area.
Argentina is the world's biggest exporter of soyoil and soymeal, and labor-related protests often cause brief disruptions at ports and crushing plants. (Reporting by Helen Popper and Maximilian Heath; Editing by Dale Hudson) (helen.popper@thomsonreuters.com; +54 11 4318 0655; Reuters Messaging: helen.popper.reuters.com@reuters.net))