(CNN) -- Five people were killed and nearly 250 injured Saturday in a series of explosions at an Albanian army depot near the capital city of Tirana.
A plume of smoke from the army depot blast rises over rooftops.
The cause of the blasts was not immediately known, although government officials said they didn't believe that they were intentional.
The explosions, which started about noon, happened as workers were trying to dismantle a stockpile of munitions, Prime Minister Sali Berisha said on his Web site.
At least 140 of the injured remained hospitalized, about a dozen in serious condition, journalist Altin Rajimi said.
The government evacuated about 4,000 people in surrounding villages, Rajimi said. Some shop owners stayed behind to protect their storefronts, fearing possible looting.
According to Albanian officials, the program to dismantle the munitions is being overseen by an American company based in South Carolina and is funded by a $30 million grant from the U.S. government, Rajimi said.
He said that some of the munitions are about 50 years old.
The U.S. Embassy in Tirana issued a statement expressing "shock and concern" over the "tragic accident" at the depot. Embassy staff planned to offer assistance to the Albanian government, the statement said.
President Bamir Topi said on his Web site that the country's National Security Council would meet to "analyze the causes of this extraordinary event, to face consequences, to take measures and to prevent similar situations from happening in the future."
Topi visited some of the victims at a military hospital earlier in the day.
The size of the stockpile is unclear, but government officials said that about 6,000 metric tons of munitions have been deactivated. E-mail to a friend