Women's accessories sold by some of the world's most popular online shopping firms contained toxic substances sometimes hundreds of times above acceptable levels, authorities in Seoul said Wednesday.

Chinese giants including Shein, Temu and AliExpress have skyrocketed in global popularity in recent years, offering a vast selection of trendy clothes and accessories at stunningly low prices that have helped them take on U.S. e-commerce titan Amazon.

The explosive growth has led to increased scrutiny of their business practices and safety standards, including in the EU and South Korea, where officials conducted inspections of items sold by online platforms.