Thefts of oxygen mounted as Mexico reported its highest daily death toll since the coronavirus pandemic began, with 1,584 deaths confirmed.
There was also a near-record one-day rise in new virus cases of 18,894.
The Mexican Social Security Institute reported that an armed man burst into a government hospital in northern Sonora state around noon on Tuesday and stole seven oxygen tanks.
The institute said the man pointed a gun at a hospital employee, demanded to know where the oxygen was kept, and took four empty canisters and three full ones.
Authorities in the city of Navajoa are looking for the man and and another suspect who drove off in a car carrying the tanks.
Also on Tuesday, police in the town of Tultepec, just north of Mexico City, chased down a small freight lorry carrying 44 oxygen tanks, after the lorry was reported stolen.
Two suspects were detained at the scene.
The consumer affairs agency launched an online campaign under the slogan Return Your Tank, For The Love of Life.
With hospitals in Mexico City and other states overwhelmed by a wave of Covid-19 cases, many families have turned to treating their relatives at home with supplementary oxygen, creating spot shortages of tanks and oxygen for refills.
But once patients recover, the agency said, many people simply keep the canisters just in case someone else falls ill.
“By doing this they are depriving other patients of something they need at a given moment, and cannot get,” the agency said.
Mexico has seen almost 1.67 million confirmed coronavirus infections and almost 143,000 test-confirmed deaths related to Covid-19.
With the country’s extremely low testing rate, official estimates suggest the real death toll is closer to 195,000.
“This theft was able to be carried out through the dishonesty and greed of a member of the hospital’s vaccination staff,” the department said in a statement.
The army has been given responsibility for transporting and guarding vaccines in Mexico, but a private security firm was apparently in charge inside the hospital.
Before Tuesday, Mexico had received only about 750,000 doses of the Pfizer vaccine, and several people have been sanctioned for cutting lines to get doses.
Mexico’s total amount so far is enough to vaccinate about half of the country’s 750,000 front-line medical personnel, all of whom will need two doses.