MEXICO CITY (Reuters) – Hundreds of Cuban doctors and nurses who were sent to Mexico City to help respond to the coronavirus pandemic could stay longer if cases keep rising, a senior government official said.

In May, 585 healthcare workers from the island nation arrived in Mexico City, epicenter of the pandemic in Mexico. It marked one of the largest medical crews that Cuba, which dispatches doctors around the world, has sent to tackle the pandemic.

Mexico City Health Minister Oliva Lopez said the Health Institute for Wellbeing (Insabi) is paying the Cuban health ministry 135 million pesos ($6.03 million).

The agreement was designed to end July 31, “but with the possibility of extension,” Lopez said in an interview on Friday. “We must deeply consider the dynamics of the epidemic.”

Biomedical engineers and epidemiologists have also been deployed, she said.

Mexico City has almost 37,000 confirmed cases of coronavirus, about 25% of the national total.

Mexican health officials have said the country is short about 6,600 doctors and 23,000 nurses to properly respond to the pandemic. Despite having hired more than 2,000 doctors and nurses, Mexico City still does not have enough health personnel, Lopez said.

Cuba has agreements with almost 70 countries to send doctors and other medical professionals.

Few details about the deals are known, but under an agreement with Brazil that was in place through 2018, the Cuban government kept 80% of what it charged for each doctor, according to Brazilian health officials.

United Nations officials said in November that the conditions under which Cuban doctors work could be considered “forced labor”. But Lopez defended the use of Cuban health care workers.

“I have seen the criticism (of the Cuban program), but the role they play in the city is fundamental,” she said.

($1 = 22.3768 Mexican pesos)