UPDATE (1/9): Officials say they now know what sparked a five-acre fire near a Brownsville landfill Monday afternoon. 

Brownsville Interim Deputy Fire Chief Rick Najera said a worker was welding on the property when the dry grass caught fire.

Firefighters were called back Tuesday to put out some hot spots that re-ignited. 

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BROWNSVILLE – Brownsville fire crews are monitoring a grass fire, trying to make sure the embers don’t reignite.

The fire is under control, but crews want to make sure the fire doesn’t reach the city’s landfill.

Roughly four acres of brush and railroad ties were burned after a fire broke out around 4 p.m. on the 1800 block of Medford Drive near Ruben Torres Blvd on Monday.

Crews say some tires were also in the mix, but they were quickly put out. 

Brownsville Office of Emergency Management and public works were also on the scene to help fire crews.

One of the difficulties with fighting the fire was trying to get access to it. Crews brought in a drone to help get a look at where the fire was burning.

“Our main concern is that back area towards that corner. We don’t want the fire to jump towards the landfill area. So we’re going to get a good aerial view of the area that’s burning so that we can either access to extinguish that or see if there is access to get to that fire,” explained Brownsville Interim Deputy Fire Chief Rick Najera.

The fire was under control by 7 p.m. Najera tells CHANNEL 5 NEWS the city plans to place a burn ban this Thursday.

With low humidity and the ground dry, he says these conditions are optimal for fires to easily burn and spread.

Brownsville fire is investigating the cause of the brush fire. We’ll pass along any new information as it becomes available.