The Chinese prime minister, Li Keqiang, who took office last month, summed up the challenges Friday.

“To come to grips with economic policy, we must both keep a steady footing and focus on upgrading,” Mr. Li told a group of economists and business executives in Beijing, in comments reported Sunday by Xinhua, the state-run news agency.

“Since the start of the year, China’s economic performance has, over all, made a steady start, and this will help to stabilize everyone’s expectations,” he said. “But at the same time, we must see that there are still quite a few unstable and uncertain factors in the domestic and international environment, and deep-seated problems are constantly arising.”

The flood of data Monday highlighted some of the uncertainties ahead.

The pickup in growth in the past few months had been mainly the result of a rush of government-mandated infrastructure spending, as well as relatively firm exports. Liquidity also has been ample — so much so, in fact, that some analysts have warned that the resulting buildup of debt carried substantial risks, including asset price bubbles and potentially destabilizing defaults.

Much of the new liquidity, however, appears to have been absorbed by borrowers seeking to service debts, rather than used for new investments or to take on new projects, according to Mr. Zhang of Nomura. He added that that might have been one reason that the first-quarter data had come in so much weaker than expected.

Economic activity may also have been held back by policy uncertainties, as government and corporate decision makers awaited pronouncements from the new leadership team on important issues like the property market, shadow banking and the buildup of local government debt, analysts said.

The authorities have signaled tighter controls in recent weeks in many of those areas, leaving some analysts to worry that the effect may be to dampen economic activity further.