Steve Polkinghorn's MetroAccess ride arrives in Washington, D.C., on April 6, 2017. (Marvin Joseph/The Washington Post)

Metro’s Office of Inspector General has reopened an investigation into whether a MetroAccess contractor manipulated tens of thousands of trip records to make late arrivals appear on-time, masking performance lapses for the paratransit service for elderly riders and customers with disabilities.

The issue came to light in a previous OIG investigation, which found more than 100,000 MetroAccess arrival times had been modified in a computer system — and suggested the changes had been made with the knowledge of management. Contractors must pay Metro a penalty if they fail to meet certain bench marks, such as on-time performance.

Some details of the investigation were posted online in a semiannual OIG report to the Metro board in October.

According to the synopsis of the report, 115,681 “late” arrival times were retroactively changed to be “on time” over a period dating to June 2009.

“OIG received allegations that a contractor was manipulating data to avoid liquidated damages,” the report says. “It was alleged [MetroAccess] management was aware of this activity and did nothing to hold the contractor accountable.”

Investigators found sufficient evidence to present the case for prosecution, but authorities turned it down because of the amount of time that had elapsed, the summary says. The office also said some “circumstances exist in which changing arrival time data may be valid.”

The full report has not been publicly released and is subject to a lengthy review process by Metro’s general counsel.

But after a June report in The Washington Post detailed a steep decline in MetroAccess service and other problems, the inspector general obtained new information pertaining to alleged data ma­nipu­la­tion. The office reopened the case, according to an individual with knowledge of the matter but who asked not to be identified because of the confidential nature of the investigation.

Metro Inspector General Geoff Cherrington confirmed the probe is ongoing, but he declined to comment on the case or provide details from the previously completed report. The office declined to say when or where the prior case was presented for prosecution, which contractor was suspected of changing the records or what portion of the modified records were believed to have been improperly altered.

“We don’t discuss open investigations,” Cherrington said.

Metro spokesman Dan Stessel said the agency has taken steps to “tighten controls” after the concerns were raised by the OIG, “including formally documenting policies and procedures, and establishing quality assurance protocols.”

He said the number of records in question represents less than 0.7 percent of MetroAccess trips during the time period. More than 60 percent of the modifications occurred before summer 2011, he said.

He also explained instances in which the changing of arrival times is allowed. “Circumstances include a driver failing to log their arrival via the onboard computer, data-transmission issues that prevent the driver from logging the arrival using the computer, among others,” he said.

Stessel noted the OIG report doesn’t specify what proportion of the more than 115,000 altered entries in question were deemed to have been improperly modified.

But the new allegations are potentially significant because the MetroAccess contract is up for bid. A memo from the agency said the bidding process for the $100 million service is expected to begin this fall and be completed no later than next summer, when the current contract expires.

The service is split among three contractors — Transdev, First Transit and Diamond Transportation — with dispatch handled by MV Transportation. MV Transportation was the service provider until 2013 and also operated dispatch through the service’s call center.

An MV spokeswoman said the company was unable to comment because it had not seen the full report. Transdev, which handles 50 percent of service delivery under the contract, denied any connection to the alleged ma­nipu­la­tion.

“As an operator of [Metro] paratransit services, Transdev strictly provides door-to-door transportation and care for [Metro] passengers,” company spokesman Scott Hagen said. “All dispatch and trip information is managed and monitored through the operations control center, which is run by another vendor reporting directly to [Metro]. Transdev does not manage, retain or submit any performance data — including on-time performance information — for [Metro] and has not done so since we began providing paratransit services for [Metro] in 2013.”

First Transit and Diamond Transportation, the other service providers, declined to comment on the probe.

MetroAccess is the transit agency’s fastest-growing and most expensive service per passenger. It offers shared, door-to-door trips to passengers within a three-quarter-mile radius of the rail and bus system. MetroAccess delivered roughly 2 million trips last year.

The service has been a focus for Cherrington, who previously conducted an investigation homing in on former MetroAccess service director Omari June. June was fired from the agency in August amid an OIG probe into his alleged racial and sexual harassment of a female subordinate.

MetroAccess service came under scrutiny in 2016 after on-time performance dropped to 83 percent from 91 percent between August and October of that year. The number of missed trips more than doubled over that period, and the number of excessively late trips — defined as more than 20 minutes after the scheduled arrival — nearly tripled, from 2,956 in August to 8,138 in October.

Users of the service, Metro’s most vulnerable customers, said they were subjected to circuitous routes and excessively long trips. One passenger recounted how her roundabout ride took so long that a fellow passenger soiled herself.

Contractors are subject to monetary penalties if they miss service targets. Transdev, First Transit and Diamond Transportation were fined almost $1 million each in the months following last year’s service slide, according to Metro. Contractors were assessed roughly $560,000 in contract damages for failure to meet performance targets over the prior decade, Stessel said, citing the OIG report on data ma­nipu­la­tion.

Metro blamed the 2016 service slide on a worker shortage that left contractors with 10 percent fewer drivers than needed. No single contractor was determined to have been responsible for the decline. On-time performance had rebounded to 90 percent by September, according to figures on Metro’s website.