BlackBerry co-founders Mike Lazaridis and Douglas Fregin said they are considering making a takeover offer for the struggling smartphone maker. Lazaridis has increased his stake in the struggling smartphone maker, according to a securities filing on Thursday.

Lazaridis currently now owns 8 percent of the company. Him and Fregin has hired Goldman Sachs Group Inc. and Centerview Partners LLC to help them study their options, according to a filing today. They signed an agreement to work together on any potential offer.

A bid for BlackBerry would compete with a $4.7 billion offer from Fairfax Financial Holdings Ltd., the company's biggest shareholder, which is seeking partners to help finance a buyout.