Some gasoline stations in at least six U.S. states are experiencing temporary fuel shortages because there aren’t enough tanker-truck drivers to deliver the fuel just as summer demand rises, according to an OPIS by IHS Markit report.

Fuel-hauling companies that reduced staff during the pandemic are struggling to hire back drivers that found jobs elsewhere, leaving Florida, Iowa, Ohio, Washington, Oregon and Colorado with cases of bagged pumps and outages of regular and premium gasoline in some filling stations, OPIS said Thursday.

The supply woes are happening as demand for gasoline has risen to levels last seen before the pandemic, with the U.S. reopening after months of lockdowns. Consumption could rise above 9.7 million barrels a day in July or August, according to the report, up from about 9.4 million last week.

For now, the supply constraints have only been a cause of inconvenience for some drivers and have not yet reached the level of a crisis, OPIS said.

But the driver shortage will likely affect fuel deliveries for another 12 months, OPIS said, citing Holly McCormick, chair of workforce committee for industry group National Tank Truck Carriers.

U.S. gasoline stockpiles, meanwhile, declined last week after recent additions.