The U.S. Securities and Exchange Commission on Monday obtained an asset freeze in connection with suspected insider trading in Anadarko Petroleum Corp before the oil company agreed to be acquired by rival Chevron Corp.

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U.S. District Judge Gregory Woods in Manhattan granted the freeze over accounts linked to suspicious purchases between Feb. 8 and April 1 by unknown buyers of Anadarko securities, who the SEC said stand to make roughly $2.5 million in illicit profits, according to a court filing.

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In a separate complaint, the SEC said the traders were unknown as they used accounts located in Britain and Cyprus, making a series of “large, unprecedented purchases” of call option contracts in Anadarko days after the company began acquisition talks, and weeks before the potential agreement was made public.

“The timing, size, nature, and profitability of the Defendants’ trades, as well as the lack of prior history of significant Anadarko options trading in the subject accounts, make the trades at issue highly suspicious,” the SEC wrote.