Former Honduran President Manuel Zelaya said Friday that he had been "unjustly" detained at the Central American nation's Toncontin International Airport as he was getting ready to travel to Mexico for a seminar.
"The reason, a bag of money with $18,000, which is not mine. Now in the presence of the prosecutor," Zelaya said on Twitter.
Honduras' national public prosecutor's office said it had no information on the matter.
Zelaya, who led Honduras from 2006 to 2009 and was an ally of late Venezuelan leader Hugo Chavez, was deposed by the military in a June 2009 coup as he was preparing to hold a referendum on presidential reelection, which his opponents said was a ploy to stay in power.
He remains active in politics, and his wife ran in presidential elections in 2013.
Zelaya said he was detained at immigration control in Toncontin airport after a search of his carry-on luggage.
The former president, leader of the leftist Partido Libertad y Refundacion party, told local media that he planned to travel to Houston, Texas, on a layover before flying to his final destination, Mexico, where he is set to give a conference on Saturday.
"I don't know the origin of that money. Obviously, someone must have put it in my belongings. I have traveled 400 times, and I know that you cannot travel with that amount of money. It is necessary to investigate who put that money in my belongings," Zelaya said.
Laws aimed at controlling trafficking and money laundering allow for a maximum of $10,000 to be taken out the country, which must be declared to authorities.