At least six people are dead and three others injured following a crash between an express bus and a box truck in Upstate New York, according to police.

The crash, which occurred Sunday morning in St. Lawrence County, was described as “gruesome” by authorities. The collision between the two vehicles left at least six dead and three injured, and police are still investigating the cause of the crash.

The National Transportation Safety Board (NTSB) is sending a team to investigate the crash, which involved a rental truck and a bus. The bus was carrying passengers from an express service and the box truck was carrying a load of produce.

The identities of those involved have not been released, but the St. Lawrence County Sheriff’s Office said that the victims were from multiple fatalities.

The crash is a tragedy for the families of those involved, and authorities are urging people to drive safely and be aware of their surroundings when on the road.