The U.S. FDA has reported there have now been 138 illnesses across 25 states from an E. coli outbreak linked to romaine lettuce grown in Salinas, California.

Of that number, there have been 72 hospitalizations, with the last illness onset on Dec. 1.

Current traceback investigations have identified a common grower in Salinas, the FDA said in its Dec. 19 update.

"FDA, CDC, and California partners have deployed a team to conduct new investigations at several ranches used by this grower as we try to identify the source of the contamination," it said.

This investigation involves assessing and sampling soil, animal droppings, compost, water and other potential environmental sources at the ranches of this grower. The samples and information collected during the farm investigation will be analyzed.

It is still recommending consumers not to eat romaine lettuce harvested from Salinas. 

At this time, romaine lettuce that was harvested outside of the Salinas region has not been implicated in this outbreak investigation.