Two U.S. Air Force planes started dropping water on a huge fire over the weekend in northern Mexico, the Environment Secretariat said.
The fire, which started just over a month ago, has been burning out of control, the secretariat said.

The two C-130 Hercules planes "began the work of dropping water and non-toxic fire retardant substances" on Sunday morning in the northern state of Coahuila, where the blaze is burning on several fronts, the secretariat said.

Mexican and U.S. planes are providing support to some 1,500 National Forestry Commission, or Conafor, and Environment Secretariat personnel on the ground.

"The planes began dropping non-toxic retardants, concentrating on the fire in El Bonito," an area where it has proven difficult to fight the blaze, the secretariat said.

Mexico began making inquiries about obtaining U.S. assistance on April 6.

The U.S. Northern Command said Saturday it would send 30 Air Force reservists and two C-130s with firefighting gear to help put out the blaze in northern Mexico.

The fire is located about 100 kilometers (62 miles) south of the Texas border.

The C-130s are equipped with Modular Airborne FireFighting Systems, or MAFFS, and belong to the 302nd Airlift Wing from Peterson Air Force Base in Colorado.

The airborne firefighting system uses pressurized tanks with the capacity to hold 13,000 liters (3,434 gallons) of water and fire retardant chemicals that can be released in less than five seconds via two pipes in the plane's tail.

About 97 percent of the more than 100,000 hectares (246,913 acres) scorched by the fire has been desert shrubs.

The fire is burning around the cities of Acuña, Arteaga, Muzquiz and Ocampo, the secretariat said.