Check out the companies making headlines after the bell on Monday:
Shares of Freeport-McMoRan rose more than 1 percent in after-hours trade after oil and gas producer Anadarko Petroleum announced it would buy Freeport's deepwater Gulf of Mexico assets for $2 billion. The deal is expected to close before year's end and add 80,000 net barrels of oil equivalent per day to Anadarko's sales-volume outlook.
Anadarko also said it will use the proceeds of a public offering of about 35.3 million shares of its common stock to pay Freeport. Anadarko's stock briefly fell more than 3.5 percent after the bell.
Weight Watchers' stock dropped about 5 percent after hours as the firm announced CEO James Chambers would resign, effective Sept. 30. "I am confident that Weight Watchers has the right strategies to play a major role in helping to inspire and guide the healthier choices that transform people's lives," Chambers said in a statement. The company's stock has faced pressure recently, falling more than 54 percent this year.
Shares of Blue Buffalo Pet Products slipped more than 2 percent after it announced a secondary offering of 14.3 million shares of common stock. The firm's stocks has risen nearly 40 percent this year.
United Natural Foods saw its stock rise about 1 percent after it reported mixed fiscal fourth-quarter results. The Providence, Rhode Island-based firm posted adjusted earnings per share of 70 cents, beating a Reuters estimate of 63 cents. Revenues came in at $2.21 billion, just shy of estimates.
— Reuters contributed to this report.