The Singapore Civil Defence Force (SCDF) had contacted at least two other companies about radiation portals before it put up a public tender for the equipment in April 2011.
One of the companies was Secom, an existing vendor of the Home Team agency and the other was IPS Securex.
Secom was asked about the price and availability of walk-through radiation detectors shortly after the SCDF was told by the Home Affairs Ministry to be prepared to scan arriving passengers at Changi Airport, in the wake of the Fukushima nuclear disaster.
IPS Securex was asked to give a demonstration of its equipment.
These emerged in court on Wednesday morning during the cross examination of SCDF logistics director, Colonel Chin Lai Fong at the corruption trial of former SCDF commissioner, Peter Lim Sin Pang.
Lim, 52, is on trial for having an illicit tryst with Ms Pang Chor Mui at a carpark in May 2010, in exchange for furthering the business interests of her employer Nimrod Engineering.
At the time, Ms Pang was Nimrod's general manager.
The prosecution has charged that Nimrod, a security systems company had received prior information from Ms Pang - Lim's one-time lover - regarding the tender before it was made public in April 2011.
Defence lawyer Hamidul Haq asked Col Chin if there was any wrong-doing involved in contacting the companies before the tender was put on government bidding site, GeBiz.
Col Chin said no and added that she did not give the companies any details of exactly what the SCDF needed.
Ms Pang is is expected to take the stand as a prosecution witness during the trial.