CHENGDU, Dec. 3 -- Fifteen people were detained and 26 officials punished after a truck-bus accident killed 21 in southwest China's Sichuan Province, said local work safety watchdog on Tuesday.

The detained suspects included truck and bus drivers, three managers of a transport company and six road administration officials, said the Sichuan Provincial Work Safety Administration.

On September 15, a passenger bus carrying 24 people, including 12 students, collided with a heavy-duty truck loaded with sand and cobblestones in Dazhou City. The bus then fell down from a 5.4-meter-high bridge and was buried by sand and cobblestones from the overturned truck.

Twenty-six government officials also received different punishments and three of them were sacked from their posts, said the administration.