Ecuador President Rafael Correa has warned of diplomatic tension if an Ecuadorean is found among the victims of a Colombian raid inside Ecuador.
Ecuador broke off diplomatic ties with Bogota after the attack
Mr Correa said Ecuador would not forgive the murder of Franklin Aisalia, if he had indeed died during the raid on Farc rebels inside Ecuador.
But he said he hoped Colombia would prove this was not the case.
Ecuador has ordered a probe after the man's family said he died in the raid in which a senior Farc boss was killed.
Colombian planes bombed a camp belonging to the Revolutionary Armed Forced of Colombia (Farc) just inside Ecuadorean territory on 1 March, killing more than 20 people including the rebels' second in command, Raul Reyes.
Mr Correa broke off diplomatic relations with Bogota after the attack.
"It would be extremely grave if it is proven that a Ecuadorean died," the president said on Ecuadorean radio. "We will not let this murder go unpunished."
Colombia has apologised to Ecuador, but said the raid was necessary.