BEIJING — Drowning in debt, metals trader Sinosteel Corp. got an unprecedented lifeline last month from the Chinese government — a multibillion-dollar debt-for-equity rescue that could be the first of many for struggling state-owned companies.

China’s economy is still growing relatively quickly, but a prolonged slowdown is raising fears that companies in many industries have borrowed and invested too much, too fast, posing a serious risk for the world’s second-largest economy.

The government hailed the Sinosteel deal, in which state-owned banks agreed to accept shares in the company to repay half the $9 billion it owes, as a model for debt reduction. Analysts are more skeptical. They say such maneuvers are typical of the ruling Communist Party’s tendency to avoid bold action and support politically favored state industry.

“They are still tinkering at the edge of the problem instead of tackling it head on,” said Mark Williams, chief Asia economist for Capital Economics.

Total debt owed by companies and households in China is estimated by private sector analysts to amount to 270 percent of annual economic output — high for a developing country and close to the levels of the United States and the European Union before the 2008 crisis.

Debt has risen at double-digit annual rates since the crisis as Beijing repeatedly used infusions of credit to shore up economic growth and avoid politically risky job losses.

In 2016, lending grew by 17 to 18 percent, outpacing the rise in savings by China’s famously thrifty households, according to Standard & Poor’s. It said that leaves banks with slimmer “funding buffers.”

Explosive economic growth that peaked at 14.2 percent in 2007 helped China power its way out of previous financial quandaries. That is no longer assured now that growth has tumbled to less than half that level — at 6.7 percent for the first nine months of last year the weakest since 1990.

The bank regulator reported in October that loans on which borrowers have made no payments in 90 days had passed $300 billion.

That is equivalent to a relatively modest 2.15 percent of total lending, but private sector analysts say the true level is far higher at up to 19 percent, or nearly $2.5 trillion. They say banks fail to include loans to state companies in their count because they assume the government will bail them out.

A banking crisis like those that hit Japan and South Korea in the 1990s is unlikely because both Chinese lenders and major borrowers are state-owned, so as a last resort, the government could order creditors to keep lending and then replenish their balance sheets, economists say.