Moscow ? A car bomb exploded Saturday outside a McDonald’s restaurant in southwest Moscow that was crowded with lunchtime customers, injuring at least seven people.

Officials disagreed on whether the explosion was a terrorist act or part of the criminal underworld violence that plagues Russia.

“Without doubt it was a terrorist act,” said Igor Pimenov of the Russian Emergency Situations Ministry, noting that the homemade bomb was stuffed with shrapnel to maximize the damage.

But Valery Grebokin, a Moscow police spokesman, said at the scene that preliminary information suggested it was “a criminal act” and not the work of terrorists. He said the two-story glass-fronted McDonald’s restaurant is located outside the city center and not one of the chain’s more prominent Moscow locations.

Investigators are looking into “possible showdowns between the McDonald’s owners and its competitors,” Moscow Prosecutor Mikhail Avdyukov was quoted as telling Interfax news agency.

The explosion, which happened shortly after 1 p.m., injured at least seven people, including a 5-year-old girl many cut by flying glass from the restaurant’s front windows as they ate their meals inside, said rescue worker Sergei Tsimburtsum.

One of the injured was in extremely serious condition, but rescue workers said that the others were expected to live.