An investigation into last year’s E. coli contamination at Chipotle locations was closed Monday.

The Centers for Disease Control and Prevention says the two E. coli outbreaks tied to Chipotle restaurants are over. The most recent illness was reported to the CDC on Dec. 1, and overall has affected more than 50 people across 14 states.

But officials say they still have not been able to identify the ingredient that may have led to the outbreak because of the way the menu is designed.

Chipotle also announced its first earnings today since the outbreak. Fourth quarter revenue was down 44 percent, and shares of the company fell 8.6% in after-hours trading.

Chipotle has three locations in Torrance: 21300 Hawthorne Blvd., 3525 W. Carson Street (in Del Amo Fashion Center) and 24631 Crenshaw Blvd.