Calcutta, Jan. 23 :    Calcutta, Jan. 23:  It was business - but not as usual - at American Center on Wednesday. The morning after the killing spree outside 38/A, Jawaharlal Nehru Road, services were resumed but there were hardly any takers. The office and the United States Educational Foundation in India (USEFI) functioned 'normally', but visitors were few and far between. 'After what happened on Tuesday, there was obvious apprehension among the people,' said Rex Moser, American Center director and public affairs officer of the US consulate-general. Both American Center and the US consulate, on Ho Chi Minh Sarani, were shut on Tuesday following the dawn attack that left four policemen dead and 22 others injured. Visa services are scheduled to resume on Thursday. But it was back-to-work at the Center on Wednesday morning, with a meeting of all staff members. The attack and its aftermath were discussed in detail, with various questions being raised about security measures at 'one of the most sensitive buildings in the city'. The mood, according to Moser, was 'sombre', but there was no sign of panic. 'The staff were asked to stay vigilant and report anything even remotely suspicious. It was made clear that there is no room for complacency,' he added. Security was beefed up at the Center, with sandbag bunkers and commandos on the alert. The presence of an FBI official lent an edge to the proceedings. But students and other visitors steered clear of what resembled a war zone. The fact that this is a 'lull period' for students applying to American universities might have contributed to the fact that very few trooped into the building. According to an employee of the USEFI, however, the few who did drop by 'did not appear apprehensive', and 'went about their work as usual'. Officials at the Center expressed confidence that things would 'return to normal soon', once the shadow of another attack lifted. 'People will probably wait and watch till January 26, before resuming their normal schedule at the Center,' said an official.