Mexico City, Mexico - The Mexican navy on Thursday launched a massive search to find two boats carrying critical humanitarian aid for Cuba that went missing with nine crew members onboard.

The vessels set sail last Friday from Isla Mujeres in Mexico's southeastern state of Quintana Roo and were due to arrive in Havana on Tuesday or Wednesday this week, the navy said in a statement.

It said that there had been neither "communication nor confirmation of their arrival" in Cuba and that it has alerted naval commanders in the region and its search and rescue stations.

"The captains and crews are experienced sailors, and both vessels are equipped with appropriate safety systems and signaling equipment," a spokesperson for the humanitarian convey said in a statement to Reuters.

"We are cooperating fully with ​the authorities ⁠and remain confident in the crews' ability to reach Havana safely," the spokesperson said.

Since last week, activists from multiple countries have left Mexican ports on vessels loaded with food and other supplies for the island nation, which faces a devastating humanitarian crisis due to a brutal US-imposed embargo.

The navy did not specify the identities or nationalities of the crew members on the missing boats, but did say that it was in communication with rescue agencies in Poland, France, Cuba, and the US.

The navy is also in contact "with the diplomatic missions of the crew members' countries of origin" to cooperate and exchange information.

The navy said it was using aircraft to search the route between Isla Mujeres and Havana, and appealed to seafarers and maritime authorities in the Caribbean and the Gulf of Mexico to report any information or sightings.

President Donald Trump imposed a brutal oil blockade on Cuba in January after the US ousted Venezuelan President Nicolás Maduro, whose government had been the island's principal source of fuel.