AUSTIN (KXAN) — More than 50,000 people have signed a petition put out by a Texas environmental group calling on Whataburger to stop using polystyrene cups and containers.

Three groups plan to deliver the petition to three Whataburgers in the state Monday: one copy at its corporate headquarters in San Antonio, one at a restaurant in Corpus Christi and one at a restaurant on Guadalupe Street in Austin.

Environment Texas says about a third of Styrofoam cups end up in the environment, and animals can mistake it for food. The substance can block their digestive tracts and cause them to starve.

“Whataburger says they’re investigating alternatives, but they need to hear from customers that we want them to act now,” the petition said on the Environment Texas website. The Surfrider Foundation’s Texas Coastal Bend Chapter and are also participating in the petition delivery.

Whataburger’s Corporate Communications released a statement following the petition deliveries:

At Whataburger, we’re always looking for the best way to serve our customers and we value their feedback.  We continue to look at cup alternatives that keep drinks at the right temperature but we have a lot to consider from a quality and supply perspective when meeting our customers’ expectations. We will share any updates if we have news to share. In the meantime, we continue to urge customers to properly dispose of our cups.” – Whataburger Corporate Communications

In June, Environment Texas held a press conference calling for Thundercloud Subs to stop using Styrofoam. The company said it planned to phase out foam cups by the end of the year.