Following the latest arrests of eight Bangladeshi workers over alleged terror plots, several questions need to be asked ("Bangladeshis plotting terror attacks held under ISA"; May 4).

First, how can we be sure that the extremist message has not spread beyond this group, since the Islamic State in Iraq and Syria is expected to look to South-east Asia to establish a caliphate ("ISIS 'may set up caliphate in S-E Asia'"; April 30)?

Second, how can we be assured of the security of our infrastructure, which is built and maintained by foreign workers?

Third, would it be prudent for Singapore to draw down its dependence on Bangladesh as a source of manpower, given the rise in extremism that the country is experiencing ("Transnational links, political vacuum fuel Bangladeshis' turn to terrorism"; May 6)?

We are often assured that the vast majority of Bangladeshi workers here are not involved in terrorist activities. So, the question remains as to how to sort the wheat from the chaff.

Leong Sek Choon