CoreWeave’s shares and bonds are on track for steep weekly losses, as investors worry about how much the AI cloud provider has borrowed, Reuters reported on Friday.

By Thursday’s close, the stock was down more than 15% for the week, its biggest weekly fall in about two months. It was also on course to lose a fifth of its value in October. Shares slipped another 4.1% in premarket trading on Friday, after bouncing back 5.9% the day before.

The selling has spread to CoreWeave’s debt as well. The company is still loss-making and owes about $50bn. On Thursday, the yield on one of its bonds due in 2031 briefly rose above 16%, a level that usually signals distress.

That bond was heading for its fifth consecutive weekly decline. Meanwhile, the cost of insuring CoreWeave’s debt against default climbed past 1,000 basis points this week, a record, according to S&P Global Market Intelligence data cited by Reuters.

Most of the damage came on Wednesday, when a hotter-than-expected US inflation report raised fears that borrowing costs will stay high. CoreWeave shares fell more than 15% that day as its bond yields jumped, CNBC reported.

Elon Musk weighed in too, replying “Yikes” to investor Chamath Palihapitiya, who had warned of a private credit bubble around AI.

CoreWeave, for its part, is standing firm. In a memo to staff on Wednesday, chief executive Mike Intrator said its backlog of signed deals more than covers its debt, Reuters reported.

Markets can “misunderstand and act irrationally,” Intrator wrote.

CoreWeave does have some support behind it. Nvidia, one of its investors and its main chip supplier, has agreed to buy any of CoreWeave’s unsold computing capacity until April 2032.

Still, the worries reach beyond one company. Nebius, a rival that recently raised $4.5bn in convertible bonds, was also set for its steepest weekly fall in two months. The sell-off comes as Big Tech’s AI debt keeps climbing to pay for new data centres.