The 26-year-old driver of a truck hauling packages for the U.S. Postal Service was killed Monday after his vehicle overturned on Interstate 680 in Danville, trapping him and spilling his load on the highway.

The driver, Ravikesh Kumar of Sacramento, crashed the two-axle box truck around 3:25 a.m. in the southbound lanes of the interstate near the El Pintado Road off-ramp, California Highway Patrol officials said.

The wreck sent packages, many of them wrapped for Christmas, all over the freeway and onto the shoulder. A scooter, a Lego set, art kits and a coffee maker were among the many items strewn around the wreckage of the truck.

The crash blocked most of the southbound lanes on Interstate 680 just as the morning commute was getting under way. Two freeway lanes were closed and CHP officials issued a Sig Alert as fire crews worked to free the driver from the cab.

Kumar lost control of the truck and struck an abandoned Ford minivan on the right shoulder, said Officer Brandon Correia, a spokesman for the CHP.

“At this time it is unclear why the driver allowed his box truck to veer into the right shoulder,” Correia said, adding that the minivan was parked well off the road.

Upon hitting the abandoned vehicle, the truck flipped over and struck a metal pole, Correia added. Emergency crews pulled the driver from the wreckage and paramedics rushed him to a hospital in Walnut Creek, where he later died.

One southbound lane of Interstate 680 remained closed until midmorning as federal employees worked to clear the packages from the freeway, Correia said.

Kumar worked for a private company carrying FedEx mail headed to a San Jose postal facility for residents in the area, said Gus Ruiz, a spokesman for the U.S. Postal Service.

Postal Service employees were sifting through the packages that had been on the truck to ensure that undamaged parcels reach their destinations, Ruiz said.

The crash came on what the U.S. Postal Service anticipated being its busiest mailing and shipping day of the year for holiday packages.

“In the Bay Area, we are going to see 30 million pieces of mail (Monday) coming in to one of the four mail facilities — Oakland, San Jose, San Francisco and the Richmond facility,” Ruiz said.

The crash was one of several collisions in the Bay Area on Monday that caused gridlock on freeways and major roads.

A woman pushing a shopping cart was struck and killed around 6:30 a.m. by a truck in the northbound lanes of Lawrence Expressway at Cabrillo Avenue in Santa Clara. The northbound lanes were closed for about two hours.

Around the same time, a truck spilled a load of rocks on Interstate 280 at Highway 101 in San Francisco, causing a multivehicle crash. The collision caused a closure of both freeways during the morning commute.

Evan Sernoffsky and Sarah Ravani are San Francisco Chronicle staff writers. Email: esernoffsky@sfchronicle.com, sravani@sfchronicle.com Twitter: @EvanSernoffsky, @SarRavani