Washington ? Spinach grown outside California’s Salinas Valley got the all-clear from federal health officials Friday, but it could be days before the leafy green returns to store shelves.

An ongoing outbreak of E. coli linked to spinach has sickened 166 people in half the states as of midday Friday. That’s up from 157 victims in 23 states a day earlier, according to the Centers for Disease Control and Prevention.

For more than a week, the Food and Drug Administration has recommend people not eat fresh, raw spinach. State and federal investigators since have traced the contaminated spinach back to three California counties, and already farm inspections there are turning up possible problems.

On Friday, officials said spinach grown anywhere outside that area is safe to eat – but industry needs to figure out how to let consumers know the origin of what they’re buying before the green can return to sale, said Dr. David Acheson of the FDA’s Center for Food Safety and Applied Nutrition.

“The public can be confident that spinach grown in those nonimplicated areas can be consumed and industry is working to get spinach from these areas back on the market,” Acheson told reporters.

“I anticipate it will be fast,” he later said of that process. “Whether it will be three days, four days – I don’t know. That will be an industry determination.”

Of those infected in the outbreak, 88 have been hospitalized, including a Wisconsin woman who died. Two other deaths have been reported in suspected cases but those cases are still being investigated.

A team of 20 state and federal investigators on Friday were to visit the 10th California field associated with the contaminated spinach, said Mark Roh, the FDA’s acting regional food and drug director for the Pacific region. Inspectors were looking for standing water, animal droppings and anything else unusual, as well as assessing the sanitation practices of farm workers. They also have taken 188 water, soil and produce samples from fields and processing plants.

The team already has spotted some potential problems.

“There are some situations of concern, may I say, that would warrant some possible corrections in the near future,” Roh told reporters by telephone. When asked to elaborate, a spokeswoman broke in and said the FDA would not, citing the ongoing nature of the investigation.

States newly reporting cases as of Friday were Maryland, with three cases, and Tennessee, with one.