(Bloomberg) — Boeing Co.’s crisis of confidence gathered pace, with the share slump surpassing 25% this year after the Justice Department opened a criminal investigation into an accident that has thrown the company into disarray.

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The shares slid as much as 4.4% in New York on Monday, their biggest intraday drop since Jan. 25. Alaska Airlines — the carrier on which a fuselage panel blew out during a 737 Max flight earlier this year — confirmed the government probe. Federal prosecutors have convened a grand jury as part of the investigation, Bloomberg News reported on Monday.

The accident on the almost-new aircraft has weighed heavily on Boeing’s stock, making it by far the worst performer on the Dow Jones Industrial Average this year. Regulators have tightened oversight of the manufacturing, capping Boeing’s output as a result. On Monday, Federal Aviation Administration Administrator Mike Whitaker said he aims to define milestones with Boeing over the next 30 days, part of a three-month deadline in which Boeing must show that it’s fixed its processes.

The crisis surrounding the US planemaker and its top-selling 737 jet has gained broad public attention, compounded by a string of seemingly unrelated recent incidents and embarrassing revelations about manufacturing lapses. Boeing is facing growing scrutiny from legislators, regulators and even passengers, with Transportation Secretary Pete Buttigieg telling Fox News Sunday that the FAA will use “an enormous amount of rigor in dealing with Boeing.”

The grand jury activity, which usually includes the issuance of subpoenas for interviews and documents, is a sign that the investigation into Boeing — and whether it has criminal liability for the incident — is deepening. News of the grand jury, which was reported earlier by the Washington Post, doesn’t necessarily mean the probe will result in charges.

Bloomberg reported previously that the department was looking into whether the door plug blowout falls under the government’s 2021 deferred-prosecution agreement with the company over two previous fatal crashes of its 737 Max jetliner. It couldn’t be immediately determined whether the criminal investigation is part of that review or has now become a standalone effort.

Missing Bolts

In the Alaska Air accident, four bolts that should have prevented the panel covering an unused door opening from flying off were apparently missing, the National Transportation Safety Board found in a preliminary report. All 171 passengers and six crew evacuated the plane without serious injury.

The FAA and NTSB are investigating the accident as well as broader safety practices at Boeing. Regulators have barred the company from raising 737 output further until they’re satisfied that manufacturing quality has improved. A panel of experts in late February issued a scathing assessment of the planemaker’s safety culture.

Tensions bubbled over last week, after NTSB Chair Jennifer Homendy told a Senate panel that Boeing had failed to cooperate in its probe of the Max 9 incident. The company hadn’t provided the names of employees who worked on the Alaska Air jet, nor had it provided documentation on how the work was performed, Homendy said on March 6.

Boeing subsequently provided the names, and has since confirmed that it had no record of the work on the Max 9’s panel.

“We’re not neutral on the question of whether Boeing should cooperate with any agency. They should,” said Buttigieg at a press conference alongside Whitaker on Monday.

Read More: US Opens Criminal Investigation Into Alaska’s Midair Blowout

A number of aviation incidents unrelated to the door-panel crisis have also made headlines, adding to the public pressure on Boeing.

A two decade-old 777 operated by United Airlines Holdings Inc. lost a wheel over San Francisco last week, damaging at least one car in a parking lot, and an older-model 737 separately belched flames from its engine after ingesting some plastic wrapping.

“All this news flow doesn’t help,” Sheila Kahyaoglu, an aviation analyst at Jefferies, told Bloomberg Television on March 8 following the string of incidents involving Boeing aircraft.

On Monday, 10 passengers and crew on a Latam Airlines Group SA flight were hospitalized after the plane encountered unexpected turbulence en route from Sydney to Auckland.

The airline said the Boeing 787 Dreamliner experienced a “technical event during the flight which caused a strong movement,” the carrier said in a statement.

The airline didn’t specify the nature of the technical event.

Read More: Latam Says 10 Aboard Flight Hospitalized in New Zealand

“We are working to gather more information about the flight and will provide any support needed by our customer,” Boeing said in a statement.

—With assistance from Danny Lee, Eduardo Thomson and Keith Laing.

(Updates with comment from FAA leader in third paragraph; an earlier version corrected an aircraft type in fifth from last paragraph)

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