ATASCOSA COUNTY – First responders from different local fire departments are managing a major fire at an oilfield site just an hour southeast of San Antonio.

The Atascosa County Sheriff's Office said first responders are "still battling the fire at several tank batteries" at the oilfield site located in the 11000 block of FM 99.

Sheriff David Soward said first responders received a call around 12:19 p.m. for a tank explosion at the site owned by a saltwater disposal company on FM 99 near Fashing, Texas, which is 15 miles east of Campbellton.

The fire is believed to have started when a truck driver was hooking up tanks and because the truck was not grounded, it caused a spark igniting flames, Soward said.

Soward said there are small amounts of petroleum products in the water and that is what's burning.

The plan for first responders is to let the tanks burn out, which could last until Wednesday morning.

Soward said Texas Department of Transportation has blocked off FM 99 between county roads 405 through 409 and will remain closed through Tuesday night.

Viewers shared images and videos of the oilfield fire with KSAT.com that show large flames with thick, black smoke shooting up into the sky.

✌🏾☝🏾👌🏾 NEWS: Here's a short clip sent to https://t.co/9vJTopdcvD of the major fire at an oilfield site near Karnes City (about an hour southeast of #SanAntonio). SKY 12 is over the scene & FULL VIDEO➡️https://t.co/hzjJBOAI3f #KSATnews pic.twitter.com/259E6hhqSA — Adrian Garcia (@adrianrolgarcia) August 21, 2018

Officials are asking commuters to stay away from the area and traffic is being diverted around the area.