Chipotle Mexican Grill re-open their 43 restaurant who was closed down due to E.coli outbreak since earlier this month. After health officials in Oregon and Washington State did not find E.coli in the sample taken from the restaurants.

According to CNN, after testing hundreds of samples, the source of an E. coli outbreak linked to Chipotle restaurants in Washington and Oregon remains unknown. Officials from Washington State Department of Health said they found no traces of E. coli in tests of food samples taken from the Washington state restaurants. In Oregon, 25 food samples from Chipotle's outlets also found no E.coli, and results for few samples are still pending. Chipotle also conducted thorough test in their premises, and showed no E.coli. The restaurant said to CNN, "To date, Chipotle has received nearly 900 test results, all of which showed no E. coli,".

E.coli outbreak in Chipotle restaurants started in the beginning of this month. Some people were reported to become sick after eating at Chipotle restaurants in Washington and Oregon. As a consequence, Chipotle must close 43 of their restaurants in those states for investigation. So far, 27 people in Washington and 15 in Oregon became ill caused by the E.coli bacteria. Of all the 42 people who became ill, 14 of them are hospitalized.

Prior to this month's outbreak, in 2008, Chipotle restaurant in Kent, Ohio was implicated in a norovirus outbreak, when 400 people became ill after eating at one Chipotle restaurant. In August this year, a norovirus and suspected Salmonella outbreak occurred in California and Minneapolis location. The case in Washington and Oregon is the last of virus outbreak in Chipotle restaurant chains.

In a preparation to re-open its restaurant and prevention of such incident, NBC News reported that Chipotle has cleaned and sanitized all the affected outlets and replaced all the ingredients it uses. The restaurant whose name is derived from a native Mexican chilli, also says is working together with health officials to improve food handling processes. Chipotle also provide more audits and inspections in all of its 2,000 restaurants. 

Fox News reported that Chipotle is to replace all ingredients at the restaurants and reopen them in the "coming days." Regarding there is no E-coli found in investigation, Washington health department officials said investigations do not always identify a specific food source as the culprit, because contaminated food is at times consumed before the samples are collected. 

This Washington and Oregon case made the fourth repeated case of outbreak in Chipotle restaurant. In order to prevent another case, Chipotle has said to implement more inspections in their restaurants.