Prestage Farms is exploring alternative locations for a pork processing plant in Iowa after the Mason City Council last week nixed a package of incentives originally offered to lure the $240 million facility.

The city council, which unanimously voted in favor of the incentives in March, was deadlocked 3-3 in last week’s vote, effectively killing the project while leaving supporters perplexed at how the city could turn down one of its largest economic...