It looks as though 90% of the Apple power accessories sold on Amazon, such as chargers and cables, are fake, according to a legal document from Apple obtained by Patently Apple.

In the document, Apple claims it bought "well over 100 iPhone devices, Apple power products, and Lightning cables" from Amazon and found that nearly 90% of the accessories were fake.

A screenshot from a YouTube video shows a knockoff iPhone wall charger the user says he bought on eBay that exploded. Raymus Munt/YouTube

Apart from potentially not working as well as genuine Apple products, Apple also claims that counterfeit Apple power accessories can cause property damage and even bodily harm. The company says in the document that counterfeit accessories are often poorly built with "inferior" — and even missing — parts, and they don't go through industry-standard safety tests. As a result, they risk catching fire or sending "deadly" electric shocks to users during normal usage.

Apple is suing Amazon supplier Mobile Star, claiming it's selling counterfeit Apple power accessories. Amazon said Mobile Star was its source for the "majority" of the products Apple bought, according to the lawsuit.

According to the lawsuit, Amazon listings for the power accessories claimed they were authentic and used Apple trademarks and product images to make the products appear authentic.

It's tough to tell which Apple products are genuine on Amazon, as the listings can appear legitimate as if they were listed by Apple itself. Overall, a good indication that a product is counterfeit or poorly made is if it's too cheap to be true. If it's drastically cheaper than what Apple charges, then it's likely to be counterfeit or poorly made without the proper certifications of safety and quality.

You can also check the reviews on Amazon. If a number of people report that the accessories caught fire, started smoking, or simply malfunctioned, and the rating is two and half stars or below, it's likely to be a fake or poorly made product.

Amazon replied to Business Insider's request for comment, saying:

“Amazon has zero tolerance for the sale of counterfeits on our site. We work closely with manufacturers and brands and pursue wrongdoers aggressively.”

Apple did not immediately return requests for comment.