A construction conglomerate at the center of Saudi Arabia’s petrodollar-fueled economic boom is teetering under billions of dollars of debt, bankers and financial advisers familiar with the matter said, showing the strain of cheap oil on the kingdom and its companies.

The Saudi Binladin Group was once among the biggest beneficiaries of Saudi Arabia’s massive spending at home, paid for by the kingdom’s growing oil wealth. But in the past half year, it has hit hard times.

An executive at one of SBG’s subsidiaries said the parent company hadn’t provided any funding to the unit for more than six months, triggering a funding crunch that has stalled longer-term plans. Several subcontractors and suppliers involved in Binladin projects also haven’t been paid for months, according to the bankers and advisers who know about the company’s finances.

And at the end of February, hundreds of SBG workers took to the streets demanding unpaid wages for work in Islam’s holiest city, Mecca, a rare episode of labor unrest in the Arab world’s largest economy.

Regional and international bankers say the group is sitting on more than $30 billion in debt. The Persian Gulf’s biggest construction conglomerate has already defaulted on an unspecified number of debt repayments, said two creditors of the group.

The main reason behind the defaults, the creditors and advisers say, is that the Saudi government has failed to make payments on time for completed or ongoing construction work. The country’s finance ministry didn’t respond to requests for comment by phone and email.

Roughly three quarters of Saudi Arabia’s budget stems from the sale of oil, and crude prices have declined since the middle of 2014, leaving the government with a gaping near-$100 billion budget deficit, according to the country’s latest budget statement released in December.

“In a way this is the government saying to them: you’ve become obscenely rich during the past 20 years but for the first time the kingdom has bigger problems to contend with,” said a creditor of the Binladin group with a major regional bank.

SBG has declined repeated requests, through emails and phone calls, to discuss its situation. SBG, a family-owned company, doesn’t disclose its financial statements. The group hasn’t made any public announcements on the labor unrest or its financial health.

Some at SBG are playing down the troubles.

Two executives, including a Gulf-based banker and a manager at one of the conglomerate’s’ subsidiaries, who recently met with leading members of SBG, said the construction firm’s management remained confident it would weather current problems.

“The very key message was: There is no crisis within Binladin,” said one of the executives.

The government’s response to dwindling oil revenues—cutting back oil and utilities subsidies to ease budgetary pressures as well as big ticket infrastructure projects—appears to have hit the construction industry particularly hard.

SBG accounts for about 70% of Saudi government construction contracts by value according to some industry estimates, making it the construction group most vulnerable to a slowdown in spending.

The group has gone through turbulent times before. After the 9/11 attacks, the Binladin family name became associated with Osama bin Laden, the founder of al Qaeda. Back then, the group had to contend with lawsuits brought by family members of those killed in the attacks. Osama bin Laden, one of the SBG founder’s many sons, never played a role in the company operations, and the lawsuits were eventually dismissed.

The company managed to maintain its close ties with the Saudi leadership and continued to win large mandates, including contracts worth billions of dollars to expand the holy cities Mecca and Medina, as well as public infrastructure projects. The contracts cemented the Binladins’ place among the kingdom’s wealthiest, nonroyal families.

In financing these megaprojects, the group has accumulated significant debt, several of the company’s lenders said. Saudi banks, as well as international financial institutions, rushed to extend credit to a group that was considered the Saudi government’s preferred contractor.

That view dimmed in September last year when high winds knocked a company crane into Mecca’s holy mosque, killing more than a hundred religious pilgrims. The deadly crane accident was a public-relations disaster for Saudi Arabia, whose king is also called the Custodian of the Two Holy Mosques. The accident also strained the relationship between SBG and the country’s leadership, according to the bankers and advisers close to the group.

After the crane accident, Saudi King Salman barred SBG from taking new projects and banned top executives from travel. An initial probe by the Saudi authorities found that strong winds caused the crane to collapse. But it also attributed part of the blame to SBG, saying the “crane was in a wrong position.” SBG didn’t comment on the findings. A full investigation has yet to be completed, and there is been no update from the government since September.

The royal rebuke came as the company was trying to reel in costs and secure new lines of credit.

The group decided last year to eliminate 15,000 jobs out of a workforce of approximately 200,000, while it failed to pay some of its employees and subsidiaries, according to the bankers and financial advisers close to SBG. SBG has also been in talks with some banks to raise new funding that would allow it to finish ongoing projects and cover some immediate loan repayments but the outcome of those discussions is still unclear, according to these people.

The failure to pay some of its employees has stirred labor tensions in the kingdom where large demonstrations are rare. Hundreds of SBG workers took to the streets at the end of February to demand unpaid wages, according to a Saudi official and local media reports. Similar protests had taken place weeks before in Jeddah as well.

After police intervened, and following meetings with company representatives, the protesters obtained a guarantee they would receive their unpaid wages and also the chance to leave the country or switch employer, the Saudi official said..

“Saudi Binladin Group has failed to pay their workers for months,” said Khaled Abalkhail, a spokesman for the labor ministry. “They have been sanctioned according to regulations.” SBG didn’t comment on the unrest.

In the absence of Western-style bankruptcy courts in Saudi Arabia, bankers warn that any sort of restructuring proceedings at SBG would be lengthy and complicated. The restructuring of another family conglomerate called Ahmad Hamad Algosaibi & Bros. is still continuing after it ran into trouble in 2009.

A financial adviser familiar with the SBG situation said, “There will have to be a political solution.”

Bankers, executives and advisers close to the group say it is unlikely SBG will ever be allowed to go under, despite the severely strained relationship with the Saudi government following the crane accident.

“It’s too big to fail,” said a creditor at a Persian Gulf bank company who is close to SBG. “It’s an integral part of the Saudi system so they will find a solution,” the person said.