Los Angeles ? Taco Bell Corp. launched a newspaper ad blitz and sent its president on a string of media interviews Tuesday to persuade customers that its food is safe – even as the cause of the E. coli outbreak linked to the fast-food chain remained a mystery.

In an open letter to customers published in USA Today, The New York Times and other newspapers, Taco Bell President Greg Creed said he would support the creation of a coalition of food suppliers, competitors, government and other experts to explore ways to safeguard the food supply chain and public health.

The executive underscored the safety mantra in media interviews, telling Associated Press Television that he had assured his daughter, a college freshman in New York, and her friends that Taco Bell food is safe.

“I can assure you, I would not tell my daughter that unless I absolutely believed it,” Creed said.

Taco Bell spokesman Rob Poetsch said the safety issue was not limited to the Mexican-style food chain.

“Based on the information we have today … we believe that this issue is not isolated to Taco Bell and that there is more need to ensure a safe food supply from the farm to the table,” he said.

Neither Creed nor Poetsch provided further details about how an industry safety coalition might work. Representatives of other fast food chains did not immediately return calls seeking comment.

Bryan Silbermann, president of the Produce Marketing Association, a trade group that represents restaurants, farmers and other companies in the produce supply chain, said such an industry coalition already exists.

The group was formed two years ago and has been particularly active since September, when three people died and more than 200 became ill because of a spinach-related E. coli outbreak.

“The largest restaurant and supermarket chains have been active in this process,” Silbermann said. “As far as I’m aware, Taco Bell has not been involved.”

Irvine-based Taco Bell, a subsidiary of Louisville, Ky.-based Yum Brands Inc., ran ads in a number of papers in New Jersey, New York, Pennsylvania and Delaware, where an outbreak of the bacteria has sickened 67 people who ate at the chain’s restaurants.

The chain’s effort to reassure customers was complicated Monday, when the U.S. Food and Drug Administration said it could not confirm that scallions were the cause of the problem, as previously suspected, and that it was not ruling out any food as a possible culprit.

A sample of white onions taken from a Taco Bell restaurant in New York was found to be positive for a strain of the bacteria that hasn’t been linked to any cases of illnesses in the U.S. within 30 days, the FDA said.

Poetsch said the company believes its food is safe because green onions were removed from use last week and restaurants have been sanitized. No additional cases of Taco Bell patrons falling ill with E. coli have been reported since Dec. 2, according to the FDA.

Some fans of the chain weren’t concerned about getting sick.

“Even if they don’t know what caused the outbreak, Taco Bell restaurants are probably safer now than before because of all the scrutiny they’ve received,” said Bruce Brandywine, 41, who was one of eight people in line at lunchtime at the Taco Bell in DeWitt, a suburb of Syracuse, N.Y.

Brandywine, a plumber, said he eats at Taco Bell about once a month. He planned to keep eating there, unless another episode of E. coli sickness is reported.