The deaths of at least 50 people found in or near an abandoned truck in San Antonio on Monday was one of the worst episodes of migrant deaths on the southern border in recent years.

The journey north for migrants crossing into the U.S. from Mexico is usually dangerous and sometimes fatal. Smugglers often transport large numbers of people in trailers, vans or S.U.V.s through remote areas in sweltering weather. And in recent years, dozens of migrants have died in crashes while traveling north.

Here are some of the deadliest vehicle chases, single-car accidents or heat-related deaths involving smuggled migrants:

• In 2003, sheriff’s deputies discovered the bodies of 17 migrants, including a 7-year-old boy, inside an overheated trailer truck in Victoria, a city in southern Texas. Officials located the trailer at a truck stop and found that the migrants trapped inside had attempted to punch out air holes so they could breathe. Another migrant who was in the trailer later died at a hospital.

• In 2012, a Ford pickup carrying more than 20 undocumented migrants struck two trees, killing 15 people.

• Ten men died in San Antonio in 2017 after riding in a tractor-trailer packed with as many as 200 migrants, and nearly 30 more were hospitalized. For hours, the people in the trailer did not have water, fresh air or food. The driver was sentenced to life in prison.

• An S.U.V. packed with undocumented migrants crashed in rural South Texas in 2019 after it was chased by police. Six people died. The vehicle had veered into a ditch in rainy weather.

• In March 2021, 13 people were killed in a remote stretch of Southern California when a crammed Ford Expedition drove into the path of a tractor-trailer.

• Last August, at least 10 people died and 20 others were injured when a van crashed in South Texas.

Miriam Jordan and Eliza Fawcett contributed reporting.