Five people died and seven were injured in a rear-end collision between a sleeper bus and a semi-trailer truck Saturday in northwest China's Xinjiang Uygur Autonomous Region.

Three drivers and one passenger died on the scene. Another passenger died later in the hospital, said the Chinese Communist Party Committee of Bayingolin Mongolian Autonomous Prefecture in a statement.

The seven injured, including four in critical conditions, have been hospitalized, it said.

The semi-trailer truck collided into the bus at 5:30 a.m. Saturday at Bayingolin Mongolian Autonomous Prefecture.

The bus was going to Urumqi from Hetian city.

Police initial investigation showed that the three drivers were Hetian citizens and their bodies have been sent back to Hetian. One dead passenger, 29, was from Tailai county of northeast China's Heilongjiang Province.

Police are investigating the cause of the accident.