Present article has conducted an investigation on imported covid19 cases of India, detected after declaration of lock down. They are marked as hidden travellers, who are detected later during 1-2 weeks of lock down. Impact of those travellers on selective 15 states, having large numbers of cases, has been investigated. Among them 5 states has faced a noticeable effect on their data profile, although its overall effect in country level is quite negligible. Those 15 states are classified into 3 categories depending upon the latest data of new cases with respect to the peak value of sigmoid functions. Based on the optimistic predicted curves, on-going lock down period will probably help for getting marginal values of new cases for KL, HR, JK, TN and AP but the remaining 15 states might need a third phase of lock down or alternative preventive measures.