A loose lid on a rail utility box is suspected of causing a light-rail train to derail Thursday in downtown Minneapolis, forcing Metro Transit to halt service between Target Field Station and U.S. Bank Stadium for more than eight hours.

No one was injured in the derailment, the third in Metro Transit history for trains in service. As the evening rush hour came and went, downtown trains remained out of commission. Around 7 p.m., the derailed westbound Blue Line train was placed back on the tracks, and after a final inspection, trains began moving again about 7:35 p.m.

The three-train car jumped the tracks on S. 5th Street between 2nd and 3rd avenues S. shortly after 11 a.m. It buckled and came to rest under the skyway connecting the CenturyLink building and U.S. Bank Plaza. Through the day, the scene attracted hundreds of passersby who stopped to gawk and take photos.

No major damage to the train, the track or overhead power lines was reported, and replacement buses shuttled passengers to light-rail stations all day.

Preliminary indications are that the lead car passed over an insecure lid on a rail access box — a shoe-size utility box that houses electrical equipment — during routine maintenance and jostled it loose, then the wheels on the second car got stuck, said Metro Transit spokesman Drew Kerr.

Light-rail derailments have been unusual since the Blue Line began service in 2004 and the Green Line in 2014. In September 2014, a Blue Line car derailed between Terminal 2 of the Minneapolis-St. Paul International Airport and the Mall of America because of debris on the LRT tracks. No one was injured, and hundreds of commuters were transferred onto buses.

In March 2011, another Blue Line train derailed before midnight between the Nicollet Mall and Hennepin Avenue stations. At the time, Metro Transit said the mishap was weather-related.

‘There was a jolt’

On Thursday, maintenance work was being done between passing trains by an unidentified contractor. Lids were to be placed back on the boxes, which are similar to manholes, but one was not properly secured, according to Metro Transit spokesman Howie Padilla. The work was part of maintenance that has been ongoing since last summer.

It was unclear how many passengers were on the train when it derailed. Passenger Jim Kaju, who was on the train when it slid off the tracks just west of City Hall, said the experience was unsettling. The train ended up straddling both eastbound and westbound tracks. “It was moving at a slow speed, barely going, when there was a jolt and the train stopped abruptly,” he said.

Witness Paul Klauda, a sports editor at the Star Tribune, said the train started to buckle as it crossed 3rd Avenue S.

“A bike courier next to me on the corner of 5th and 3rd started running away from the train with his bike, and I followed. For a moment you thought the whole thing could come unhitched,” he said.

A few minutes after the train stopped, an announcement could be heard from inside the train saying, “Folks, we had a major disruption of our service here,” Klauda said.

Passengers were evacuated without incident, Padilla said.

Replacement buses were brought in to shuttle passengers between Target Field and U.S. Bank Stadium. Blue Line trains operated normally from U.S. Bank Stadium to Mall of America, and Green Line trains continued running from the stadium to Union Depot in St. Paul.

But the derailment and ensuing shutdown affected passengers using both the Blue and Green lines, because both serve downtown Minneapolis. Average weekday ridership for the Green Line in 2016 was 39,386, while the Blue Line reported 30,337 passengers during the same period.

Hydraulic equipment was brought in to jack up the wayward rail car and push it back on the tracks, Padilla said. A similar contingency plan using replacement buses is ready during Super Bowl festivities in late January and early February, should light rail experience a lapse in service, he said.

“We are having regular conversations about contingency plans for service during the Super Bowl,” he said. “We are not worried about it, but we are preparing for every scenario not only for replacement buses, but returning trains to service as quickly as we can.”

Staff writer Janet Moore contributed to this report.

Tim Harlow • 612-673-7768