Mexico’s navy said on Thursday it had activated a search-and-rescue operation in the Caribbean to locate two sailboats carrying humanitarian aid to Cuba after the vessels failed to arrive in Havana as scheduled.

In a statement, the navy said the two boats left Isla Mujeres, in the Mexican Caribbean state of Quintana Roo, last week bound for Havana with nine crew members of different nationalities on board.

The vessels had been expected to arrive between 24 and 25 March, but there had been no communication from them and no confirmation of their arrival, the navy said.

The two missing boats are part of a broader grassroots aid effort for energy-strapped Cuba, which has been suffering prolonged power outages and a deepening economic crisis after the US tightened an embargo on oil and other goods. A separate vessel from the convoy arrived in Havana on Tuesday.

Volunteers in Mexico last week loaded boats with rice, baby wipes, beans, baby formula, medicine and other supplies as part of the “Nuestra America Convoy,” a non-government initiative seeking to deliver food, medicines and energy-related goods to the island.

“The captains and crews are experienced sailors, and both vessels are equipped with appropriate safety systems and signalling equipment,” a spokesperson for the convoy said in a statement to Reuters. “We are cooperating fully with the authorities and remain confident in the crews’ ability to reach Havana safely.”

Mexico also established contact with maritime rescue coordination centers in Poland, France, Cuba and the United States, as well as diplomatic representatives of the countries of origin of those on board, the navy said.