BlackBerry Ltd.'s founders Mike Lazaridis and Doug Fregin are considering an offer to buy back the Waterloo, Ont.-based smartphone maker, they said in a regulatory filing Thursday. The founders said they are looking at “all available options” including “a potential acquisition,” and have hired Goldman Sachs and Centerview Partners LLC as advisers. BlackBerry is also talks with Cisco Systems Inc., Google Inc. and SAP AG about its possible sale and plan to go private, Reuters reported earlier this month. The Wall Street Journal similarly reported this month that New York-based private equity firm Cerberus Capital Management LP was looking at a possible acquisition. BlackBerry said in September that it is seeking a sale through a tentative offer from Toronto investment firm FairFax Financial Holdings Ltd., which proposes to lead investors in an acquisition for $4.7 billion US, or $9 US per share. The company said this week it will close its Halifax office, eliminating 300 to 350 jobs. The cuts are part of a restructuring process to reduce its global workforce by about 40 per cent.