Between 5 and 15 people were killed in a Texas fertilizer plant explosion that injured more than 160 people and leveled buildings for blocks.

Thursday morning officials were going from house to house looking for survivors.

They evacuated nearly half the town.

The mayor of the town of West, Texas says some firefighters who were battling the blaze when the blast happened were still missing Thursday morning.

Mayor Tommy Muska says there were five or six volunteer firefighters battling the blaze at the West Fertilizer plant when the explosion happened just before 8 p.m. Wednesday.

Muska, who is a volunteer firefighter himself, says not all of his fellow firefighters are accounted for. He says the blast knocked his helmet off and shattered the windows of his nearby home.

The plant was cited for failing to obtain or to qualify for a permit in 2006. The Texas Commission on Environmental Quality investigated West Fertilizer on June 20, 2006, after receiving a complaint of a strong ammonia smell. Agency records show that the person who lodged the complaint said the ammonia smell was “very bad last night” and lingered until after he or she went to bed.