At least two people died and nine others were injured on Thursday when a passenger train collided head-on with another train during a test run just outside Santiago, Chile’s capital.

Investigators are examining the cause of the crash, which resulted in one train car landing on top of a car from the other train.

The eight-car freight train, carrying 1,346 tons of copper, was also filled with passengers. The other train had 10 workers on board conducting a speed test, according to the state rail company.

Authorities have not disclosed the identities of the two people killed. Among the nine injured were four Chinese nationals who are receiving medical care at hospitals near the crash site in San Bernardo, Chile.

“We must determine the causes and take appropriate actions,” Transportation Minister Juan Carlos Muñoz told The Associated Press.