CRESSON (CBSDFW.COM/AP)A fire at a North Texas chemical plant following an explosion last week is being allowed to burn itself out before authorities search for a missing worker who’s presumed dead.

Cresson Mayor and Assistant Fire Chief Bob Cornett said Sunday that conditions at the 15,000-square-foot Tri-Chem Industries plant are “just too hot” and “just too dangerous.” He says rains Saturday night aggravated chemicals and acids at the site about 25 miles  southwest of Fort Worth.

Cornett says the plant is being guarded to ensure no one enters and that state and federal environmental and workplace officials are standing by to assist local authorities.

According to the Hood County Fire Marshal, rescuers have performed a number of searches looking for 27-year-old Dylan Mitchell, but they had to be abandoned because of toxic smoke and fumes.

Investigators believe a worker dragging his foot along the floor while chemicals were being mixed sparked Thursday’s explosion. That worker is hospitalized with critical burns. Another worker was treated for lesser injuries.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)