ST PETERSBURG, Russia, Feb 19 (Reuters) - Russian police investigating an explosion at a McDonald's <MCD.N> restaurant in St Petersburg doubt it was an act of terrorism, media reported on Monday. The Sunday night explosion injured six people and rekindled memories of a wave of attacks by Chechen separatists across Russia in the 1990s. But there have been no big attacks outside the Caucasus region for more than two years and a St Petersburg police spokesman said there was no immediate reasons to believe that the McDonald's bomb was one of those. "At the moment the main priority version is hooliganism," the spokesman told Interfax news agency. Police have said they were checking other McDonald's restaurants in St Petersburg for explosives. City prosecutor Sergei Zaitsev said late on Sunday the explosion at the outlet on Nevsky Prospect, the city's main thoroughfare, had been caused by an unidentified substance.
