LUCKNOW, India (AP) — An explosion ripped through a makeshift fireworks factory in northern India on Saturday, killing at least five people who were making the pyrotechnics for a popular festival to be held next month, police said.

The owner of the factory was among those killed in the blast, which also injured 20 people, said senior police superintendent Praveen Kumar.

Some of those injured were in critical condition, including a schoolgirl who was passing by on the street when the explosion occurred on the outskirts of Lucknow city, in the state of Uttar Pradesh.

Authorities were investigating the cause of the blast.

The small, makeshift factory was manufacturing fireworks for October's Diwali festival, an ancient Hindu celebration also known as the "festival of lights."