Source code is a version of computer software which is usually much easier to read and understand than the end version in a finished product, and could be used to reverse engineer parts of the product.
For example, the Frostbite engine, which hackers claim to have the source code for, is a powerful game creation tool used in dozens of games, from FIFA to the Battlefield series and several recent Star Wars games from EA.
The source code for the engine could hold significant value for an unscrupulous developer willing to copy it, or for those making cheat codes and hacks for games.
But it is unlikely that any mainstream competitor to EA would ever use such stolen data.
It is the latest in a string of high-profile gaming company hacks.
In November last year, Capcom, the maker of Street Fighter and Resident Evil, suffered a ransomware attack which may have revealed the personal information of up to 350,000 people.
And in February, Cyberpunk developer CD Projekt Red suffered another ransomware attack which resulted in the source code for several games being stolen and auctioned off online.
In that case, the hackers claimed to have sold the data for more than $7m (£4.9m), though it is not clear if the sale actually happened.