(UPDATED COVERAGE, 3:30 p.m.) Despite advising the Subway sandwich chain that fresh produce is suspected in a recent salmonella outbreak, Illinois health officials had yet to establish a definite link more than five weeks after the first illness was reported.

UPDATED: Illinois salmonella cases rise to 80

As of June 17, the number of illnesses linked to the Subway sandwich chain has risen to 80.

“At this time, we have not identified the source and are diligently working with our local health departments, (the Food and Drug Administration, the Centers for Disease Control and Prevention) and Subway Corporation to find the source and prevent any future illnesses,” said Melaney Arnold, communications manager for the Illinois Department of Public Health.

“We do not have a time estimate of when this will wrap up,” she said.

Arnold did not comment on why investigators suspect produce and not meat or dairy products, whether salmonella was found in restaurants or how far down the supply chain the contamination was traced.

In discussions with its vendors, Subway has reinforced the importance of getting regular inspections by third-party auditors and government agencies and of following industry Good Agricultural Practices and Good Manufacturing Practices, as well as the chain's own Gold Standard Food Safety and Quality policy, according to a June 17 company statement.

An FDA official had no comment June 17.

After diners began reporting illnesses, Subway replaced lettuce, green peppers, red onions and tomatoes from restaurants in 26 Illinois counties.

The latest date reported for hospitalization was May 30. The ages of those sickened range from 2 to 79.