Check out the companies making headlines after the bell Monday:
Shares of Valeant Pharmaceuticals popped briefly after-hours Monday, reversing some losses after reports of credit downgrades and regulatory investigations sent shares lower late in the session.
Credit ratings agency Moody's announced a review of Valeant's ratings for downgrade Monday afternoon, and separate reports from Bloomberg and The Wall Street Journal linked Valeant to a potential SEC probe.
Marathon Oil's stock dipped in extended trading after the company announced an offering of 135 million shares of common stock to bolster its balance sheet. The move comes as historically low oil prices have strained the energy industry.
Shares of Workday slid slightly after the HR software maker reported a widening loss in the fourth quarter. The company's net loss hit $81.1 million, or 42 cents per share from $59.5 million, or 32 cents per share, a year earlier, according to Reuters, beating expectations slightly. Higher spending on sales, marketing and product development hurt the company after a tumultuous earnings season for cloud-based "software as a service" firms across the enterprise technology sector.
Diplomat Pharmacy shares tumbled after hours, despite beating earnings and revenue expectations for the latest quarter. The company, which focuses on treatments for rare chronic conditions, reported light forward guidance for 2016 earnings.
Shares of Anacor Pharmaceuticals also fell after the company posted a loss of 43 cents per share, more than the 29 cents Wall Street expected, according to the Associated Press. Anacor makes drugs for conditions like dermatitis.
—Reuters, the AP and CNBC's Seema Mody and Meg Tirrell contributed to this report.