Sixteen migrants and asylum seekers from several countries have tested positive for coronavirus in Mexico's northern border state of Tamaulipas, the state government said Monday.

Fourteen of the infected migrants from Honduras, Mexico, Guatemala, Cuba and Cameroon were staying at a migrant shelter in the city of Nuevo Laredo, across the border from Laredo, Texas. They are in isolation.

The Tamaulipas state government said a migrant deported from Houston, Texas had entered the same shelter without knowing that he had coronavirus. Migrants now make up about 10 percent of the state's 193 coronavirus cases.

"The state government, foreseeing the situation of multiple contagions of COVID-19 among the migrant population, has asked the federal government through official channels to transfer out of Tamaulipas the migrants who are stranded on the border," the state said in a statement.

A medical staff member of Global Response Management takes the temperature of a migrant patient at a migrant encampment in Matamoros, Mexico, where more than 2,000 people live while seeking asylum in the US [Daniel Becerril/Reuters]

Hundreds of migrants and asylum seekers remain in Nuevo Laredo, and in the Tamaulipas border city of Matamoro, an estimated 2,000 people live in a squalid tent camp, waiting for their court hearings a short distance away in Brownsville, Texas.

US Immigration and Customs Enforcement (ICE) says that more than 100 migrants at 25 detention centres have tested positive for COVID-19.

Mexico's federal government has so far officially recognised only one case of coronavirus infection in a migrant, at the church-run shelter in Nuevo Laredo. The federal National Immigration Institute did not immediately respond to a request for comment.

The Catholic-run shelter is expected to release the results of further tests on the migrants.

Tamaulipas also said another migrant who was deported from Atlanta, Georgia - and who had not gone to the shelter - tested positive after being detected at a border checkpoint. He has been returned to his home state of Michoacan for care.

The US government said Monday it will continue to quickly expel migrants it encounters along the border for at least another month in response to the COVID-19 outbreak. The move has been slammed by immigrant rights groups.

An order issued by the US Department of Health and Human Services said the policy should be kept in place for another 30 days to help reduce the spread of the virus in detention centres. The new order extends the policy until May 20.

US officials last month launched the new policy, saying it would be dangerous for US Customs and Border Protection (CBP) to detain people because of the potential spread of the virus. As a result, CBP has been turning away thousands of migrants and asylum seekers.

Deported Guatemalans test positive

In recent weeks, concerns have mounted about the spread of the highly contagious virus through deportation proceedings.

Guatemala President Alejandro Giammattei said on Sunday that a total of 50 migrants deported by the US to the Central American country had tested positive for coronavirus. The country has temporarily suspended the flights.

Guatemalan migrants walking towards a bus after being deported from the US in Guatemala City, Guatemala [Fabricio Alonso/Reuters]

Just 400 detainees in the US out of more than 32,000 had been tested as of last week, according to testimony that Matthew Albence, the acting director of ICE, gave Friday to a US congressional committee. The House Committee on Oversight and Reform said that Albence "also confirmed that ICE does not routinely test detainees before deporting them".

More than 1,600 people deported from the US to Guatemala over the last month were allowed to go home and into voluntary, unenforced quarantine. Fears are rising that it may have seeded the Central American nation with an untold number of undetected cases, increasing its vulnerability to the pandemic.