MENDON, Mo. — Three people were killed and several others were injured Monday when a passenger train traveling from Los Angeles to Chicago struck a dump truck and derailed in a remote, rural area of Missouri, officials said.

Two of the people who died were on the train and one was in the truck, Missouri State Highway Patrol spokesman Cpl. Justin Dunn said. It was not immediately clear exactly how many people were hurt, the patrol said. Several hospitals said they had received patients and were expecting more.

The Southwest Chief was carrying about 243 passengers and 12 crew members when the collision happened near Mendon, Amtrak said. The Highway Patrol said seven cars derailed.

The collision occurred at a rural intersection on a gravel road with no crossing arms, Dunn said. A 911 call about the collision came in at 12:43 p.m. and the first emergency responders arrived within 20 minutes, he said.

An Amtrak passenger train lies on its side after derailing Monday near Mendon, Mo. Dax McDonald via Associated Press

Helicopter video of the site from KMBC-TV in Kansas City showed rail cars on their side as emergency responders used ladders to climb into one of them. Six medical helicopters parked nearby were waiting to transport patients.

Close to 20 local and state law enforcement agencies, ambulance services, fire department and medical services responded, Dunn said.

Passengers on the train included 16 youths and eight adults from two Boy Scout troops who were traveling home to Appleton, Wisconsin, after a backcountry excursion at the Philmont Scout Ranch in New Mexico, but no one in the group was seriously injured, said Scott Armstrong, director of national media relations for the Boy Scouts of America. The Scouts administered first aid to several injured passengers, including the driver of the dump truck, Armstrong said.

High school students from Pleasant Ridge High School in Easton, Kansas, who were headed to a Future Business Leaders of America conference in Chicago, were also aboard, Superintendent Tim Beying told The Star.

The Southwest Chief takes about two days to travel from Los Angeles to Chicago. Mendon, with a population of about 160, is about 84 miles northeast of Kansas City.