(Reuters) - Seagate Technology said its board approved a plan to buy back up to an additional $2.5 billion worth of common stock.

The amount is equal to about 18 percent of the company's market capitalization.

The disk drive company said the latest buyback plan increases its total current buyback authorization to $3.5 billion.

Seagate said it expects to fund the share repurchase through a combination of cash on hand, future cash flow from operations and potential alternative sources of financing.

Shares of the company were trading marginally down at $30.85 in extended trade. They closed at $31.09 on Thursday on the Nasdaq.

(Reporting by Anil D'Silva; Editing by Sreejiraj Eluvangal)