Shares of Jet Airways India Ltd. headed for their lowest level in almost four years after income-tax authorities conducted a “survey” at its offices, the latest trouble for an airline that’s been struggling to pare losses.

“The company is fully cooperating with the authorities and responding to the queries,” the airline part-owned by Abu Dhabi’s Etihad Airways PJSC, said in a filing on Friday. It said the officials have been examining its books since Sept. 19 and didn’t provide further details.

The stock fell as much as 7.6% in Mumbai on Friday, the biggest intraday loss since Aug. 10. The decline was compounded by an incident Thursday, when pilots flying one of its aircraft forgot to maintain cabin pressure during ascent, causing injuries to many passengers.

Mumbai-based Jet Airways, which last month reported its biggest quarterly loss since 2015, is seeking to raise funds and reduce debt as part of a turnaround plan. The carrier is among those finding it tough to make money in the Indian market, where competition has driven fares below cost. It has said salary payments to pilots will be staggered over two installments each month for three months.

Once among the leaders in India—the world’s fastest growing aviation market—Jet Airways has now lost share to a slew of budget carriers like IndiGo and SpiceJet Ltd.

India’s Registrar of Companies, which is under the Ministry of Corporate Affairs, has also started an initial inquiry into potential wrongdoings at the airline, such as diversion of cash, people familiar with the matter said last month. Jet Airways then said it wasn’t aware of any probe initiated by the government.