MEXICO CITY (Reuters) - A group of Cuban migrants reported as kidnapped at Mexico’s northern border has been released, a newspaper reported on Monday, as officials continued probing the disappearances of other migrants in the region.

Thirteen Cubans kidnapped in the border city of Reynosa in Tamaulipas were released on Sunday and appeared to make their way to the United States, newspaper El Universal said, citing a family member of a kidnapped migrant who was sent a video of the people walking to the U.S. border.

The newspaper reported that a criminal group demanding ransom kidnapped several of the migrants a week before, holding them with nine other Cuban migrants who were previously kidnapped.

The state government said it had not received any kidnapping reports related to the group. The Cuban embassy did not immediately respond to a request for comment.

President Andres Manuel Lopez Obrador told a regular news conference on Monday that officials were still looking for 22 people, thought to be migrants, who were kidnapped by armed men from a bus in early March in Tamaulipas.

Violent clashes among criminal gangs in the state have led to high rates of murders and disappearances for years.

Lopez Obrador also said that Mexico is making progress in reaching an agreement with the United States on investment in Central America and Mexico to reduce migration.

The United States will commit billions of dollars toward development in the region as part of a plan to strengthen local economies and discourage migration, officials said in December.