The number of confirmed E. coli food poisoning cases linked to Chipotle Mexican Grill Inc (CMG.N) restaurants in Washington state and Oregon rose to 40 on Thursday, as health safety officials continued searching for the source of the contamination. Washington lowered its count to 28 after additional testing ruled out one case that was suspected to be linked to the outbreak. Eight Chipotle restaurants in the greater Seattle and Portland areas are linked to the outbreak.