Some of the migrants who peeled off from a caravan and decided to stay in northern Mexico are protesting delays in granting residency visas and are threatening to go to the U.S. border to seek asylum.

Mexican Sen. Maria del Carmen Ojesto said Wednesday that 15 of the Central Americans are on a hunger strike in the northern state of Sonora to demand visas they say they were promised.

The migrants have said that "if the promises are not kept, about 100 people will reconsider (staying in Mexico) and go to Tijuana to request asylum" in the U.S., she said.

Mexico's National Immigration Institute said about 120 people had staged a demonstration outside immigration services offices in Hermosillo, the capital of Sonora state, demanding all applications be approved.

The institute said the requests for humanitarian visas or asylum would only be approved in accordance with existing laws. The institute says 76 migrants are working legally in Mexico, out of a total of 182 visa requests made. An additional 106 are still being reviewed because they lack necessary information.

Mexico already granted many migrants on the caravan transit visas to reach the U.S. border.

Earlier this month nearly 200 caravan members went to Tijuana and started to make their cases to U.S. officials that they be allowed to live in the United States. Many said they were fleeing gang violence in Honduras and El Salvador.

More than half of the Central Americans and others who filed asylum requests in Mexico in 2017 had not received an answer by early this year. Mexico says its application procedure was slowed down by damage to its offices caused by a Sept. 19 earthquake.