Venezuela's state-run oil company PDVSA declared a maritime emergency on Tuesday after Bernhard Schulte Shipmanagement (BSM) disclosed plans to return 10 tankers over unpaid fees, according to a document from the state-run firm and sources.BSM, operator of a portion of PDVSA's tanker fleet, last month confirmed its crews would abandon the tankers Rio Arauca and Parnaso, which were held in Portugal over unpaid fees to a shipyard and port authority. A third vessel also operated by BSM, the Icaro, separately was seized in Curacao by a group of shipping firms claiming unpaid bills from PDVSA.(Reuters reporting by Marianna Parraga; Editing by Jeffrey Benkoe)