A train collided with a herd of elephants in Sri Lanka on Wednesday night, killing at least six of them, according to Sri Lanka Police.

No passengers were injured, but wildlife veterinary officers are treating a female elephant and an injured calf in the city of Giritale, Sri Lanka’s state-owned Daily News reported Thursday.

The Meenagaya train hit the herd at the 140 km mark between Minneriya and Galoya railway stations at around 11:30 pm Wednesday, Daily News reports.

“According to a statement released by the Department of Wildlife Conservation, Railway Department officials, police, and wildlife officers swiftly coordinated efforts at the scene. Further investigations into the incident are underway to determine the circumstances surrounding the collision,” Daily News reports.

According to the World Wildlife Fund (WWF) Sri Lankan elephants are the largest and the darkest of the Asian elephants. Their herd size ranges from 12-20 individuals and the oldest female typically leads the herd.

Elephants are a popular tourist attraction and hold symbolic, cultural and economic importance for Sri Lanka, WFF states. But co-existing with humans continues to be an issue as their forest habitats are cleared for human infrastructure and agriculture.

Similar incidents have happened before. The Associated Press reported that in October at least two elephants were killed when a train carrying thousands of gallons of fuel hit a herd in northwest Sri Lanka in the town of Minneriya, about 200 km from the capital, Colombo.

Minneriya National Park is home to the world’s largest known gathering of Asian elephants and draws many tourists, according to the park’s website.

The train driver told the Associated Press in October that the herd of nearly 20 elephants suddenly tried to cross over the railway track.

“There was about 10 meters (32 feet) between us. So, we couldn’t do anything. We pressed the breaks to their maximum capacity, but there was nothing much we could do. At least four elephants were knocked down.” drive N.W. Jayalath told the Associated Press.