MEXICO CITY — Mexican customs officials have seized purported vials of the Sputnik V COVID-19 vaccine en route to Honduras that the Russian entity that bankrolled the vaccine’s development said Thursday were fake.

The seizure came aboard a private plane in the Gulf coast state of Campeche, according to a statement from Mexico’s tax agency late Wednesday.

Customs agents and soldiers found 1,155 vials containing more than 5,700 doses inside two coolers packed with ice and sodas. The crew and Honduran passengers were turned over to the Attorney General’s Office.

Mexican officials did not identify the doses as fake, but the Russian Direct Investment Fund said in a statement Thursday that after reviewing photographs of the packaging, they determined the vaccine to be fake.

“Analysis of the photographs of the seized batch, including the design of containers and labels, suggests that it is a fake substance which has nothing to do with the original vaccine,” according to the RDIF statement. “The shipment’s procedure was also in violation of packaging and transportation protocols for the official Sputnik V vaccine.”

It said the Russian Health Ministry would cooperate with Mexican authorities to analyze the contents of the vials.

The RDIF also drew geopolitics into the mix, saying, “This is an example of possible provocations against Sputnik V just as Russian officials warned last week. Mexican government stopped and prevented this provocation possibly aimed at discrediting Sputnik V vaccine through shipment of fake vaccine.”

Russian state-funded news agencies last week cited an anonymous high-ranking Kremlin source saying that “the U.S. and its allies” are plotting “a large-scale information campaign aimed at creating a bias” towards Russian scientific products designed to counter COVID-19.

The source said that the alleged plan is to paint Sputnik V as ineffective and dangerous, including by “staging mass deaths, allegedly as a result of using” the vaccine.

Mexico started vaccinating people with Sputnik V last month and has received 400,000 doses to date.