Fire engulfed part of a chemical plant northeast of Houston on Friday evening, sending thick black smoke high into the sky, a statement from Arkema, the owner of the plant, confirmed. It was the same facility where, on Thursday, a chemical storage trailer exploded, setting off a fire. Flooding from Harvey, once a Category 4 hurricane that hit southeast Texas last week, had knocked out the refrigeration system needed to keep the chemicals stable.

Two trailers were on fire Friday evening, Rachel Moreno, a spokeswoman for the Houston Fire Marshal’s office, confirmed.

“There are six more trailers there with the potential to do the same,” she said of the plant in Crosby, Tex., but she could not predict whether any more trailers were immediately at risk. The company said in the statement Friday evening, “We will likely see additional incidents. Please do not return to the area within the evacuation zone until local emergency response authorities announce it is safe to do so.”

The company has previously said that the smoke from the burning chemicals can irritate the eyes, nose and lungs, but it was not clear how much of a health threat the new release posed.