The state's announcement came the same day that the U.S. government said it will continue to quickly expel migrants it encounters along the border for at least another month in response to the COVID-19 outbreak.
Under the U.S. policy change spurred by the virus, the U.S. government has sent some 10,000 Mexicans and Central Americans back to Mexico, according to data from the U.S.Border Patrol.
The situation led Tamaulipas to ask the administration of President Andrés Manuel López Obrador to not accept anymore Central Americans delivered back across the border to Mexico from the United States. Tamaulipas undersecretary for legal and governmental affairs Gloria Elena Garza Jimenez said the agreement between the two countries had no legal foundation.
Fifteen 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 Nazareth migrants shelter in Nuevo Laredo said three of the infected migrants were minors. Of the 15, three were hospitalized but were released back to the shelter. More tests have been done at the shelter but no other cases have been confirmed.
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% of the state's 193 coronavirus cases, causing frustration in Tamaulipas.
"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.
Hundreds of migrants remain in Nuevo Laredo and in the Tamaulipas border city of Matamoros, an estimated 2,000 people live in a squalid tent camp, waiting for their court hearings a short distance away in Brownsville, Texas.
The U.S. Immigration and Customs Enforcement (ICE) says that more than 100 migrants at 25 detention centers have tested positive for COVID-19. Guatemala claims that 44 migrants deported from the U.S. tested positive.
Dr. Joseph McCormick, a physician and public health expert in Brownsville, Texas, across the border from Tamaulipas, said it's important to track where infected migrants have been.
"We know the virus is out there in all the smallest communities in our area," said the former CDC epidemiologist and current director of The Hispanic Health Research Center (HHRC) on the Brownsville campus of the UTHealth School of Public Health.
"Sending people off to these vulnerable countries is going to make whatever the situation is there, which we probably don't know much about, much worse," he said. "And eventually it will come back to bite us because people who may be headed to the border who are not infected may get infected and may come back and re-infect our country. For every person who is apprehended and sent back there are probably 10 who get across the border and get somewhere. This is not a smart process."
Mexico's federal government has so far officially recognized 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.