Passengers on the commuter rail line linking New England’s two largest cities are braced for up to half an hour of extra travel time Friday after a train car derailed near the Lansdowne station Thursday afternoon and damaged a section of the track.

Preliminarily, system operator Keolis said the derailment is “believed to be caused by human error in not setting a switch properly.”

Roughly 200 passengers were on the train set when an empty car derailed along the Framingham/Worcester Line at about 3:40 p.m. Thursday. No injuries were reported and the exact cause remains under investigation by Keolis and the MBTA.

Passengers were moved to another train, Keolis said, and were returned to Boston. Media clips of the incident showed passengers disembarking and walking along the rail bed. Bus service to Worcester was provided and some trains were able to operate between Worcester and Boston Landing station.

“Yesterday’s incident was particularly frustrating because we did not have – it blocked equipment headed out to Worcester so we were not able to provide a great deal of service,” MBTA General Manager Steve Poftak said Friday morning on WCVB-TV. “We had to replace it with bus service, which I know is particularly inconvenient for our customers.”

Poftak added that he will let the investigation play out.

“We obviously want to understand fully exactly what happened here and make sure it does not happen again,” he said.

Keolis said its workers made “good progress” overnight and had the section of track that was damaged open by 5 a.m. Friday. Riders along the east-west line between Worcester and Boston were advised to prepare for delays of 20 to 30 minutes for some trains.

Thursday’s incident happened less than three weeks after the commuter rail system was held out as a bright spot in a report that eviscerated the MBTA’s safety record.

The Keolis-operated commuter rail “is performing well and does not face many of the challenges that were identified on the transit side of the house,” an independent panel commissioned to study safety at the MBTA concluded in a report that faulted the T’s subway and light rail system for a culture that does not do enough to emphasize safety for employees or riders.

Keolis Commuter Services beat out former system operator Massachusetts Bay Commuter Railroad Company in 2014 for a $2.69 billion, eight-year contract to operate the MBTA’s commuter rail system. The contract expires in 2022 but has two separate two-year extensions.

Earlier this month, a commuter rail coach detached from its train near South Station during the morning commute on Dec. 2 after experiencing mechanical issues.

The company said Thursday’s derailment was a “low-speed, upright derailment,” which it explained means that the train was traveling slower than the maximum-allowed 30 miles per hour for that stretch of track and that while the train car made contact with the ground, it remained in an upright position.

On Friday morning, the Worcester line was also hampered by faulty equipment. The first train of the morning, which is scheduled to leave South Station at 4:40 a.m., was canceled Friday due to “a mechanical issue with the main engine” and sent delays rippling throughout the already-affected line.