Rigrodsky & Long, P.A. announces that it is investigating potential claims against the board of directors of SemGroup Corporation (“SemGroup” or the “Company”) (NYSE: SEMG) concerning possible breaches of fiduciary duty and other violations of law related to the Company’s receipt of a proposal from Plains All American Pipeline, L.P. (“PAA”), to acquire the Company for approximately $1.24 billion in cash (the “Proposal”). Click here to learn more and to discuss your shareholder rights: http://investigations.rigrodskylong.com/semgroupcorporation-semg/. The Proposal contemplates PAA’s acquisition of all of the outstanding shares of common stock of SemGroup for $24.00 per share in cash. The investigation concerns the board of directors’ process for consideration of the proposed transaction, whether SemGroup is acting in its shareholders’ best interests by refusing to enter into negotiations with PAA, and whether the proposed consideration to be paid to SemGroup shareholders would be fair and adequate. According to today’s Proposal, SemGroup’s board of directors has refused to engage in talks despite PAA having raised its Proposal price from $17.00 per share in March 2010 to the current offer of $24.00 per share. If you own the common stock of SemGroup and purchased your shares before October 24, 2011, if you have information or would like to learn more about these claims, or if you wish to discuss these matters or have any questions concerning this announcement or your rights or interests with respect to these matters, please contact Seth D. Rigrodsky, Esquire or Noah R. Wortman, Case Development Director, of Rigrodsky & Long, P.A., 919 N. Market Street, Suite 980, Wilmington, Delaware, 19801, by telephone at (888) 969-4242, or by e-mail to email@example.com. Rigrodsky & Long, P.A., with offices in Wilmington, Delaware and Garden City, New York, regularly litigates securities class, derivative and direct actions, shareholder rights litigation and corporate governance litigation, including claims for breach of fiduciary duty and proxy violations in the Delaware Court of Chancery and in state and federal courts throughout the United States. Attorney advertising. Prior results do not guarantee a similar outcome.