The officials said first responders stole electronics and money from an ATM. Another official said police guarding the site overnight attempted to a take a safe from a bank in the burned-out arrivals hall, which also houses several foreign currency exchange shops.
All four officials who described the alleged looting are close to the investigation.
The fire-fighting response to Wednesday's inferno was criticized as slow and inadequate, but officials could not definitely say the looting was carried out by firefighters. One official said there was now behind-the-scenes finger pointing taking place between police, fire department and army. Another official said specialized police units had attempted to steal the safe overnight.
The criminal investigations policeman for the airport, Joseph Ngisa, said he hasn't received formal complaints of theft and that police are waiting for affected institutions to report what they lost in the fire.
International flights, meanwhile, resumed Thursday as officials improvised immigration and luggage routines.
Kenyan officials, assisted by members of the FBI, investigated the cause of the fire.
One of the security officials who spoke to the Associated Press said the investigation had ruled out terrorism and was now trying to determine if the fire was intentional or accidental.