A husband and wife in a pickup died in a crash after their vehicle was hit by one of several large hay bales that toppled off a passing semitrailer truck in southeastern Minnesota, authorities said.

The incident, which the State Patrol said "could have been prevented," occurred Saturday morning along Houston County Road 9 northeast of the city of Houston.

Teresa E. Erickson, 52, of Houston, died the next day, the patrol said. Her husband, Dale O. Erickson, 59, was hospitalized in La Crosse, Wis., and died Tuesday.

According to the patrol:

The semi was heading south on County Road 9 and approaching a curve near County Road 21 when "it lost large, round bales of hay."

One of the bales struck the northbound pickup, causing Dale Erickson to lose control of the vehicle. It crashed into a ditch to the right and caught fire.

The rig's driver, Randall C. Hongerholt, 49, of Houston, was not injured.

The State Patrol is investigating the crash. Drivers are required to safely secure their load.

"Commercial vehicles, and all vehicles, are required to secure their load in a manner that prevents any of its load from dropping, shifting, leaking, blowing or otherwise escaping from the vehicle," said Patrol Lt. Tiffani Nielson. "This fatal crash, unfortunately, is exactly why we have these laws in place — to prevent injuries or death. This was a very tragic crash, and a family is grieving a terrible loss that could have been prevented."

Hay bales vary greatly in weight, depending not only on dimensions but density. A federal study analyzed seven deaths in Minnesota in the mid-1990s associated with large hay bales and found that the bales ranged from 750 to 1,500 pounds.