AT&T, Sun Microsystems and Swiss banking-software vendor Temenos were among the technology companies with offices in the two towers destroyed in the 11 September attack.
AT&T said it had 10 employees working on the 51st floor of the North Tower - the first tower to be hit - and a larger networking team working in the basement. All escaped.
Temenos also managed to evacuate all of its workers from the 52nd and 84th floors of the North Tower, the company said.
Sun, meanwhile, is still trying to establish the safety and whereabouts of its 300 World Trade Centre employees, a spokeswoman for the company said. The operation was a flexible field office housing sales and service personnel, which makes establishing which employees were in the building particularly difficult.
Likewise, the employment Web site CallCentreCareers.com sent out an alert announcing that its ASP, CareerEngine Network, was destroyed in the blast. CallCentreCareers.com said it had been unable to ascertain the status of CareerEngine's staff, who were based on the 21st floor of the South Tower. CareerEngine's Web site, hosted off-site by Globix, was still online on Wednesday, 12 September, but the company's phone lines are down.
The fate of some 1,000 people employed by the financial services firm Cantor Fitzgerald and its subsidiary, eSpeed, remains unclear. The companies occupied several of the uppermost floors of the North tower. Cantor Fitzgerald has to date been unable to determine how many employees were in the office at the time of the blast and whether or not they were safely evacuated.
The New York-based software firm Computer Associates (CA) had 140 employees working in a sales office and demo centre a short distance from the World Trade Centre. All were safely evacuated, with only a few minor injuries, said vice-president of human resources Kevin Long. CA has closed its office "at least through to the end of the week", Long said, although major damage to the company's infrastructure is not expected.
CA is anticipating the loss of data that had not yet been backed-up; most staff in the Manhattan office worked on laptops, which were left behind in the hurried evacuation. But off-site back-ups ensured that no critical data was lost, and client information is secure, Long said.
Companies with infrastructure damaged in the attack are beginning to implement contingency plans and restore lost services. AT&T's network coped "quite well", with calls routed away from the damaged nodes at the World Trade Centre, said company spokesman Phil Coathup. AT&T's long-distance network was unaffected by the blast but overloaded by a massive call volume.
Temenos's clients and business partners have offered office space and assistance in the company's rebuilding efforts, said chairman and chief executive officer George Koukis. The company expects to have its service capacity restored to normal within the next few days, he said. The company's president of American operations held an emergency meeting on 12 September to outline Temenos's recovery plans.
Several companies in New York joined the relief efforts by offering office space to displaced firms and employees. In one instance, the online retailer Bluefly has offered to donate 9,000 square feet of empty office space to displaced companies.