A Central Bureau of Investigation (CBI) official said Tejinder Singh reached the probe agency's office around 11 a.m. and was questioned till 5 p.m.
"In the six-hour-long questioning, the agency, which has registered a preliminary enquiry in connection with complaint submitted by the army chief, questioned Tejinder Singh on three documents - visitor's register, record of discussion of the army and documents related to Tatra," said the official.
The agency also questioned the retired officer on the meeting which took place Sep 22, 2010 at the army chief's office.
Tejinder Singh has already refuted the allegations against him and filed a defamation case against the army chief and other officers.
The CBI Tuesday indicated that there was enough evidence to proceed with the army chief's allegation that he was offered a bribe by Tejinder Singh in September 2010 for clearing a tranche of 600 Tatra trucks.
The probe agency is likely to convert the preliminary enquiry into a regular case (first information report), the official said.
The army chief had in his 22-page complaint to the CBI alleged that Tejinder Singh offered him a bribe of Rs.14 crore on behalf of Vectra chief Ravi Rishi. Rishi has denied any wrong doing.
The CBI recorded the army chief's statement as part of the informal probe. Gen. V.K. Singh told the agency that he had apprised Defence Minister A.K. Antony about the bribe offer and also noted it in his personal diary.
A CBI official said that they ascertained the date of Tejinder Singh's meeting with Gen. V.K. Singh and gathered material to prove that the file related to Tatra truck procurement was there on the table of the army chief on the day the alleged bribe offer was made.