Samsung will blame Galaxy Note 7 explosions on “irregularly sized” batteries and manufacturing problems, according to a new report from The Wall Street Journal. The South Korean company has promised to reveal the results of its internal investigation on Monday.

It wasn’t on the market for long, but the Note 7 was Samsung’s best smartphone to date. It had the looks, it had the features, and it had stellar specifications. There was very little to complain about… until some units started overheating and catching fire.

As you’re probably already aware by now, Samsung was forced to recall all units twice, and eventually ceased production of the Note 7 just a few months after it made its debut. Since then, the company has been investigating the cause of the problem.

According to WSJ, which cites “people familiar with the matter,” there were actually two root causes. Some batteries were “irregularly sized,” while others suffered manufacturing defects.

“Samsung, the world’s largest smartphone maker by shipments, conducted the investigation with three quality-control and supply-chain analysis firms that it hired to help it in its independent investigation,” the report explains.

Ironically, many of the batteries used in the Note 7 were manufactured by Samsung SDI, the company’s own battery division. These are the ones that were irregularly sized. Those with manufacturing defects were produced by Hong Kong-based Amperex Technology.

Both Samsung and Amperex have declined to comment so far, but Samsung has confirmed it will make its findings official on Monday. It’s thought the whole fiasco will end up costing the company around $5 billion.

Now that Samsung knows exactly what caused the Note 7 to overheat, it will be easier to address the issue. That should mean there will be no such problems with the upcoming Galaxy S8 — or the next-generation Galaxy Note (presuming there is one).