The U.S. Transportation Department began an investigation of how Boeing Co.’s 737 Max was certified to fly passengers before the latest crash in Ethiopia involving the new jet, according to a person familiar with the probe.

The investigation was prompted by information obtained after a Lion Air 737 Max 8 crashed shortly after takeoff from Jakarta, Indonesia, on Oct. 29, said the person, who wasn’t authorized to speak about the investigation and asked not to be named.

The investigation has taken on new urgency after the March 10 crash of an Ethiopian Airlines 737 Max 8 near Addis Ababa that killed 157 people. It is being conducted in part by the department’s Inspector General’s office, which conducts both audits and criminal investigations in conjunction with the Justice Department.

Boeing shares were down 1.77 percent to $372.28 Monday in New York, heading toward a new low since the deadly crash of Ethiopian Airlines Flight 302 on March 10.

Separately, the Wall Street Journal reported that a grand jury in Washington, D.C., on March 11 issued a subpoena to at least one person involved in the development process of the Max. And a Seattle Times investigation found that U.S. regulators delegated much of the plane’s safety assessment to Boeing and that the company in turn delivered an analysis with crucial flaws.

A possible criminal investigation during an aircraft accident investigation is highly unusual. While airline accidents have at times raised criminal issues, such as after the 1996 crash of a ValuJet plane in the Florida Everglades, such cases are the exception.

U.S. Federal Aviation Administration employees warned seven years ago that Boeing had too much sway over safety approvals of new aircraft, prompting an investigation by auditors who confirmed the agency hadn’t done enough to “hold Boeing accountable.”

The 2012 investigation also found that discord over Boeing’s treatment had created a “negative work environment” among FAA employees who approve new and modified aircraft designs, with many of them saying they’d faced retaliation for speaking up. Their concerns pre-dated the 737 Max development.

In recent years, the FAA has shifted more authority over the approval of new aircraft to the manufacturer itself, even allowing Boeing to choose many of the personnel who oversee tests and vouch for safety. Just in the past few months, Congress expanded the outsourcing arrangement even further.

“It raises for me the question of whether the agency is properly funded, properly staffed and whether there has been enough independent oversight,” said Jim Hall, who was chairman of the National Transportation Safety Board from 1994 to 2001 and is now an aviation-safety consultant.

At least a portion of the flight-control software suspected in the 737 Max crashes was certified by one or more Boeing employees who worked in the outsourcing arrangement, according to one person familiar with the work who wasn’t authorized to speak about the matter.

Both Boeing and the Transportation Department declined to comment about that inquiry.

In a statement on Sunday, the FAA said its “aircraft certification processes are well established and have consistently produced safe aircraft designs,” adding that the “737 Max certification program followed the FAA’s standard certification process.”

In one of the most detailed descriptions yet of the relationship between Boeing and the FAA during the 737 Max’s certification, the Seattle Times quoted unnamed engineers who said the planemaker had understated the power of the flight-control software in a System Safety Analysis submitted to the FAA. The newspaper said the analysis also failed to account for how the system could reset itself each time a pilot responded — in essence, gradually ratcheting the horizontal stabilizer into a dive position.

Boeing told the newspaper in a statement that the FAA had reviewed the company’s data and concluded the aircraft “met all certification and regulatory requirements.”