The United Steelworkers Union Local 5668 rejected a contract proposal from Constellium Rolled Products.
There was no word from the union about how close the vote was. The union has not yet made a statement about the vote.
The company issued a statement after the vote calling the contract fair. The offer also introduced a new healthcare plan, in which hourly employees would begin contributing to premiums in 2014, at rates about half of the national average.
"As we said when we presented the offer, the proposal offered employees real economic benefit, while ensuring their families still have quality, affordable healthcare benefits," CEO Kyle Lorentzen said in the news release.
"For a facility that has struggled and suffered significant losses in recent years, we believe this was a very competitive offer. Over the next few days, we hope to get a better sense of what caused the offer to be voted down, including whether there was some misunderstanding about the package being offered. At that point, we'll assess next steps."