WASHINGTON (AP) – The Agriculture Department will speed up warnings about contaminated meat in the future, officials said Thursday, as they sought to quell criticism of an 18-day delay in seeking the recall of millions of pounds of tainted ground beef.

Briefing reporters, department officials acknowledged that they knew as early as Sept. 7 that frozen hamburger patties could be contaminated after preliminary tests indicated the E. coli bacteria strain O157:H7.

They said it was impossible to seek a recall without conducting a more sophisticated test to confirm the original results, but said they would reevaluate what USDA can do better to warn the public sooner.

“Let me be clear from the beginning, at this point we weren’t able to take action based on the initial test,” said David Goldman, assistant administrator of the USDA’s Office of Public Health Science.

Still, “this agency is not completely satisfied with the time elapsed and the issuance of the recall,” he said. “We will be reviewing data related to this recall as well as our own protocol to determine how we might improve.”

Richard Raymond, the department’s under secretary for food safety, then added: “It’s a policy we will be changing here.”

The department’s response comes after news reports disclosed an Agriculture Department e-mail showing the department knew on Sept. 7 about possible contamination but waited 18 days before concluding Topps Meat Co. should issue a recall.

The recall that began Sept. 25 was soon expanded to comprise 21.7 million pounds of hamburger produced by Topps, based in Elizabeth, N.J.

A Florida teen was hospitalized with kidney failure in August, and the meat her family bought was tested by the USDA.

The e-mail – from federal inspector Kis Robertson, an employee of the USDA’s Food Safety Inspection Service – was provided by the teen’s family lawyer, Scott P. Schlesinger, on Thursday. The e-mail was reported Wednesday by The Chicago Tribune.

“They should have recalled immediately. That’s not even a maybe,” Schlesinger said.

Asked about the delay, Topps spokeswoman Michele Williams referred questions to the USDA.

In the news briefing, Agriculture officials said the Sept. 7 preliminary results yielded 13 negative samples of the questionable ground beef and just one positive result.

Subsequently, USDA scientists conducted a more sophisticated test, known as the Pulsed Field Gel Electrophoresis, that took an additional seven days due to some unexpected glitches.

Those results became available on Sept. 14, but USDA did not act immediately because the suspected meat had been opened in the consumer’s home, raising the question of whether it was contaminated there.

As of noon Wednesday, 29 people in eight states, including Maine, had E. coli infections matching the strain found in the Topps patties, the Centers for Disease Control and Prevention said. None has died.

The Agriculture Department is investigating in an attempt to find the source of the E. coli strain, which is harbored in the intestines of healthy cattle.

The CDC reported these states and number of cases: Connecticut, 2; Florida, 1; Indiana, 1; Maine, 1; New Jersey, 6; New York, 9; Ohio, 1; and Pennsylvania, 8.

The recall represents all Topps hamburger products with either a “sell by date” or a “best if used by date” between Sept. 25 this year and Sept. 25, 2008.

All recalled products also have the USDA establishment number EST 9748, which is on the back panel of the package or in the USDA legend. A full list of the recalled products is available at http://www.toppsmeat.com.