SACRAMENTO — Five months after the produce industry rolled out new guidelines in an effort to bring safer spinach and lettuce to America's tables, another spinach recall is shining a spotlight on what that approach can — and can't — ensure.

The Salinas Valley company that yanked back 68,000 pounds of spinach this week, fearing salmonella contamination, says it found the problem by going far beyond the updated safety guidelines.

From that, people can reach almost any conclusion that suits their politics: We need tougher laws. Or market forces will keep our produce safe. Or the new guidelines are helping. Or they aren't.

"It's never going to be perfect. We all understand that," said Bill Marler, a Seattle attorney who specializes in food poisoning litigation. Marler argues that ultimately, tough regulation will protect consumers better than even the most vigilant companies.

Spinach and lettuce growers are hoping, instead, to prove their trustworthiness with voluntary efforts, including something called the Leafy Green Marketing Agreement, which calls for safer farming practices.

Scott Horsfall, who oversees that agreement, estimates that 99 percent of handlers — the companies that pack fresh greens from California and send them to markets or restaurants — have signed onto the pact since it went into effect April 1. The terms require handlers to do business only with growers who pledge to test irrigation water, keep animals out of fields, and take other steps to prevent contamination.

The guidelines themselves came after years of food-borne disease outbreaks traced to the Salinas Valley, most recently last fall when spinach contaminated with E. coli killed three and sickened 200.

Horsfall estimates that more than half the handlers covered by the leafy greens agreement are also doing additional product testing that's not required by the pact.

Among them are Metz Fresh, a growing and shipping company based in King City in Monterey County. It started pulling bags of spinach off the assembly line and testing samples back in October, said company spokesman Greg Larsen.

That "final product testing" was the procedure that tipped Metz Fresh to potential salmonella on Aug. 24, he said. The company began contacting shippers and retailers that day, telling them to hold off on moving any more of the spinach, which was headed to stores and grocers in 48 states and Canada.

Larsen said Metz Fresh didn't issue a public recall right away because it wanted to do a second, more thorough round of testing.

Those tests were done Tuesday, and Metz Fresh worked into the evening with the Food and Drug Administration to craft a recall notice, Larsen said. The notice itself wasn't made public until very late Tuesday night or early Wednesday morning, he said.

By then, the company had tracked down about 90 percent of the 8,000 cases of spinach it had shipped, and it had not received any reports of people becoming ill.

On Friday, Larsen said, the company still wasn't certain what happened to the other 10 percent. It doesn't know if anyone ate it, how much was sold or in what states, he said.

One of the biggest questions is why Metz Fresh didn't hang onto its spinach until the test results were in.

Such a test and hold approach is "the smartest move," said Horsfall of the leafy greens group.

Said attorney Marler: "Testing without holding tells you whether a product is contaminated or not, but if it is, it's already out your door and you have a problem. I don't think it's wise to test it and ship it."