"We really don't know what's going on," said Bobby McLean, director of the state Department of Agriculture's Bureau for Food Safety.
Earlier in the day, investigators had hailed the positive salmonella test as a step forward in the investigation.
The E1 salmonella strain found on the tomatoes in the Sheetz store in Greencastle, Franklin County, also can make people ill, but public health officials had narrowed the outbreak to the Javiana strain.
"Is there something else going on that we're not aware of? We don't think there is, but we're going to take a closer look at this," said Richard McGarvey, state Department of Health spokesman, after the E1 strain was detected.
Investigators believe produce caused the outbreak and are looking at Roma tomatoes and lettuce as the most likely sources, McGarvey said. Those who ate the contaminated produce fell ill with salmonellosis, which causes diarrhea, abdominal cramps and fever. Symptoms usually occur within 12 to 72 hours of infection and last up to 10 days. The disease is rarely fatal.
There were 110 reported cases of salmonellosis in Pennsylvania as of Monday, linked to people who ate at Sheetz July 2-10 in 12 counties. State health officials first learned of the problem on July 9.
The first secondary cases connected to the outbreak were reported Monday in West Virginia, which has linked 18 cases to the Pennsylvania outbreak, including two who did not eat at Sheetz stores, but had contact with someone who did, said Dr. Danae Bixler, state director of infectious disease epidemiology. Two more suspected cases are under investigation, she said.
Poor hygiene can spread the illness secondarily from an infected person to others.
Her office also is investigating five cases of people who became ill after eating somewhere other than a Sheetz to see whether those cases can be linked to the outbreak or whether they are an unrelated cluster, Bixler said.
Health officials in Ohio, Maryland and Virginia said 31 salmonellosis cases there are probably linked to the Pennsylvania outbreak, but they are awaiting more test results.
Pennsylvania agriculture officials have tested more than 200 samples of food, most removed from stores owned by Altoona-based Sheetz. Only the one sample with the E1 strain tested positive for salmonella, McLean said. Some samples also were taken from warehouses that supply grocery stores and food establishments other than Sheetz and receive produce from several suppliers, including Coronet Foods Inc., the Wheeling, W. Va.-based producer to Sheetz until last Friday.
After the state Department of Agriculture told Sheetz that a different strain of salmonella was found in the bag of tomatoes other than the one connected to the outbreak, Alicia Thayer, Coronet's quality assurance manager and director of food safety, declared, "Our Roma tomatoes did not cause those people to get sick."
A four-state outbreak linked to Roma tomatoes contaminated with salmonella Javiana was traced to a South Carolina packer in 1990. The number of people sickened in that outbreak officially was listed at 176, although the actual number might have exceeded 35,000, according to a 1999 report published in Epidemiology Infections by the U.S. Centers for Disease Control and Prevention and public health officials in Minnesota, Illinois, Michigan and Wisconsin, where the outbreak occurred.
A 1993 outbreak in the same four states was linked to tomatoes contaminated with another type of salmonella, Montevideo, and also was traced to a South Carolina packer. Officially, 100 people fell ill, but more than 20,000 could have been infected, according to the report.
Investigators found that some victims in that outbreak did not become sick for at least five days -- two days longer than normally counted among salmonellosis outbreaks.
The report concluded that "similar large, geographically dispersed foodborne outbreaks are likely to go unrecognized."
Two studies sponsored by the tomato industry following those outbreaks found that salmonella spreads easily among infected tomatoes. The bacteria are absorbed into the pulp or grow on the skin. Even with proper handling and processing, the report said, "it may not be possible to eliminate salmonella contamination."
It is possible for "one bad tomato to spoil the whole bunch," the report said.
Several studies "suggest that individual consumers may be limited in their ability to decontaminate fresh produce items," according to the report.
The first lawsuit stemming from the local outbreak was filed against Coronet in federal court in Pittsburgh yesterday by James Grove, 40, of West Sunbury, Butler County, who said he was hospitalized for three days with salmonellosis after eating at two Sheetz stores in Butler County, in Renfrew and Butler.