U.S. manufacturing activity grew at a slower pace in April, restrained by shortages of inputs as rising vaccinations against COVID-19 and massive fiscal stimulus unleashed pent-up demand.

The survey from the Institute for Supply Management (ISM) on Monday showed record-long lead times, wide-scale shortages of critical basic materials, rising commodities prices and difficulties in transporting products across industries.

The pandemic, now in its second year, has severely disrupted supply chains. The ISM noted that “companies and suppliers continue to struggle to meet increasing rates of demand due to coronavirus impacts limiting availability of parts and materials.” It cautioned that worker absenteeism, short-term shutdowns due to part shortages and difficulties in filling open positions could limit manufacturing’s growth potential.

“Manufacturing is struggling to keep up with roaring demand,” said Will Compernolle, a senior economist at FHN Financial in New York.