Mexican authorities are investigating the theft of several coronavirus vaccines from a public hospital, the army said Tuesday, underscoring the challenges of distributing the shots across the crime-plagued country.

Mexico, which has one of the world's highest Covid-19 death tolls, has deployed the military to guard the vaccines and prevent them falling into criminals' hands.

The army said that the stolen vaccines were under the control of a public health institution in a hospital in central Morelos state whose security is overseen by a private company.

"This theft could have been a dishonest act of self-interest by a member of the hospital's vaccination team," it said in a statement.

The Mexican government has promised to make vaccinations available free of charge across the country of almost 129 million people -- a massive logistical challenge -- starting with frontline health workers.

There have been a handful of reported cases of queue-jumping, including a hospital manager who was sanctioned for being immunized along with his family.

Mexico has officially recorded more than 140,000 Covid-19 deaths -- the world's fourth-highest toll after the United States, Brazil and India.

The country began mass immunization on December 24 using the coronavirus vaccine developed by US drugs giant Pfizer and its German partner BioNTech, but it is constrained by limited supply.

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PFIZER

BioNTech