LONDON - Health experts say time is running out for German investigators to find the source of the world's deadliest E. coli outbreak, and some have been surprised - even shocked - at lapses in the German investigation.

Health officials are still looking for the cause of the outbreak, which began May 2.

So far, the super-toxic strain of E. coli has killed 24 people, infected 2,400, and left hundreds hospitalized with a serious complication that can lead to kidney failure. New cases are being reported every day - 94 more in Germany on Tuesday.

"If we don't know the likely culprit in a week's time, we may never know the cause," Dr. Guenael Rodier, director of communicable diseases at the World Health Organization, said in an interview Tuesday.

Experts say the outbreak could have been spotted sooner with better medical detection and immediate interviews with patients about what they ate.

German officials pointed to Spanish cucumbers as the culprit last week but had to retract that when the cucumbers were found to have a different strain of E. coli. On Sunday, they blamed German sprouts, only to backtrack a day later when initial tests came back negative.

Rodier said that the contaminated vegetables had probably disappeared from the market and that it would be difficult for investigators to link patients to contaminated produce weeks after they became infected.

Other experts were even more critical of the German investigation.

"If you gave us 200 cases and five days, we should be able to solve this outbreak," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, whose team has contained numerous foodborne outbreaks in the United States.

Osterholm described the German effort as "erratic" and "a disaster" and said officials should have done more detailed patient interviews as soon as the epidemic began. He also disputed the idea that it might be impossible to find the outbreak's source.

"To say we may never solve this is just an excuse for an ongoing bad investigation," he said. "This is like a cold murder case where you go back and reexamine the evidence."

German lawmakers have slammed the chaotic response to the outbreak, criticizing the confusing announcements and retractions.

Christine Clauss, Saxony's state health minister and a member of Chancellor Angela Merkel's governing party, said states were initially conducting their own investigations into the outbreak.

"It would be especially important to cooperate more closely and in a more centralized way in situations with a nationwide germ," she told the daily newspaper Leipziger Volkszeitung.

Karl Lauterbach, a physician who serves as health expert for the opposition Social Democrats, has repeatedly urged the government to set up a national crisis team to coordinate the work of federal and state authorities responding to the crisis.

Paul Hunter, a professor of health protection at the University of East Anglia in England, said German investigators could have picked up the outbreak sooner if doctors regularly did lab tests on patients with diarrhea - a standard practice in Britain.

"They could miss an outbreak starting until people get quite sick with severe complications," he said.

Hunter said German doctors probably realized how big the outbreak was only when the number of patients with kidney failure spiked in mid-May.