After more than a year and a half, investigators on Friday reported the cause of a gas line explosion that erupted in the middle of a south Minneapolis street.

A report by the Minnesota Office of Pipeline Safety said that the blast on March 17, 2011, at 60th Street and Nicollet Avenue S. was the result of the pipe's inability to handle the weight of the area's soil, road and traffic.

The report also says there are other high-risk locations on the pipeline system.

A representative for CenterPoint Energy, the gas line operator, said the company was reviewing the report and would respond accordingly. "Safety is our top priority," said CenterPoint spokesman Jim Bartula.

The explosion happened about 8:30 a.m. near the front of a Cub Foods store. Nobody was hurt, but the blast sent flames several stories high and damaged the road, vehicles and facilities within 350 feet. Minneapolis police and the State Patrol closed roads and part of Interstate 35W and evacuated residents.

According to the report, the pipeline failed at two couplings that separated from the pipe. Steel straps that were welded across them to prevent pipe movement broke away at the welds when the stress on the joints was excessive. It was undetermined what ignited the gas.

"Improper design and failure to install the joints in a manner that could sustain external loading experienced at this location were contributing causes to the event," the report said.

CenterPoint has identified other high-risk locations in their system and has initiated a program to weld compression sleeves over other mechanical joints, the report said.

Bartula declined to provide additional details about those locations.

"The entire system is safe," he said.

The segment of pipeline that was affected by the explosion has been replaced, Bartula said.

Nicole Norfleet • 612-673-4495 Twitter: @stribnorfleet