Nordstar B738 at St. Petersburg on Jul 31st 2014, could not fully retract gear

A Nordstar Boeing 737-800, registration VQ-BDO performing flight Y7-405 from Saint Petersburg to Norilsk (Russia) with 146 passengers and 6 crew, was climbing out of St. Petersburg when the crew did not receive indication that all gear had locked in the retracted position. The crew levelled off at FL070, entered a hold to burn off fuel and returned to St. Petersburg for a safe landing on runway 10R about 2 hours after departure.