When Boston news station WCVB began asking Massachusetts State Police for answers regarding questionable overtime shifts last fall, it would trigger an avalanche.

State Police launched an internal investigation following the inquiry. The attorney general's office would launch its own investigation. Other media outlets, including MassLive, began assailing the agency with records requests probing the police agency's finances and troopers' shifts.

Less than a year later, four Massachusetts State Troopers have been arrested, a fifth has pleaded guilty and MassLive has learned at least 10 more troopers are expected to face indictments.

But a review of dozens of internal state police files by the Boston Globe has revealed state police had clear red flags of payroll fraud at least as early as 2014 and that the agency did little about it.

The Globe report shows that state police internal affairs investigated two troopers in 2014 who were believed to be secretly working escorting funeral processions and taking cash under the table. What they also found in the process of the investigation was that the two troopers had filed for more than 30 hours a week in overtime and paid details they did not actually work.

That fact never made it into the investigators' final report, the Globe reports.

The Globe report also shows at least 67 troopers were suspected of abusing sick leave since 2011 but at most received a written warning.

Investigations by the State Police, the attorney general's office and federal prosecutors continue.

More than 40 state troopers are now under investigation in connection to the overtime scandal. MassLive has identified 28 of the troopers involved in the investigation.

Of the five troopers who have been charged or pleaded guilty, MassLive has identified $122,000 in money taken for shifts that were not worked.

In early July, federal prosecutor Andrew Lelling was asked how much total money was taken as a result of the scandals.

"At the end of the day, that's the same question as whether it's a systemic problem or not a systemic problem [within the State Police]," Lelling said. "We can't know at this stage how much money we're really talking about."

Gov. Charlie Baker, who installed Col. Kerry Gilpin as superintendent and tasked her with cleaning up the State Police, has called the scandal an "alleged scam" and a "conspiracy" that goes back "many years."

"Let me be clear that today's charges are the beginning and not the end of this federal investigation," Lelling said last month.