The TNT fireworks, which the U.S. Consumer Product Safety Commission says prematurely explode when lit, were being sold in Walmart and Kroger stores in the four states. So far three people have suffered minor burns as a result of the defective fireworks.

A spokeswoman for TNT said people who bought the defective fireworks should report them to American Promotional Events and take them back to the store for a full refund.

“The 30 days around the Fourth of July is when we see the most injuries occur,” said Ann Marie Buerkle, acting chairwoman of the CPSC, during a press conference on July 4th safety earlier this week.

Consumer fireworks, the kind people set off in their backyard versus the much larger ones meant for city- and town-wide displays, have become increasingly popular according to data from the American Pyrotechnics Association.

Of the $1.2 billion in revenue the U.S. fireworks industry saw last year, 70% of it was from consumer fireworks. That segment of sales grew 9% year-over-year. Meanwhile, growth in the display segment has remained relatively flat.

The U.S. fireworks industry is an old one. But as is the case with nearly every industry, technology has started to change how people use fireworks. Winco Fireworks has a new product called FireFly, that allows consumers to design and execute their own fireworks shows. It pairs hardware, a black box with 15 wires to connect to fuses, and a mobile app available for Apple or Android devices.