I sent an email to the manufacturer just before the new year and I got the reply from them today:
Thank you for contacting us regarding Riviana Popping Corn.
Riviana Popping Corn is manufactured on a site that handles no allergenic products.
All popping corn is sourced from suppliers that do not have allergens on site.
If we can be of any further assistance please do not hesitate to contact me.
So Girls, we have one item to add to our kids' snack options...
PS. Please feel free to pm me for the manufacturer's detail if you wish to check with them again.