PORT NECHES, Texas (CBSDFW.COM/AP) — It was more than a week ago when a pair of chemical plant explosions happened in southeast Texas, injuring three workers and damaging homes up to several miles away. Today concerns over air quality have prompted a voluntary evacuation.

The Texas Gulf Coast city of Port Neches issued the voluntary order for its 50,000 residents late Wednesday after elevated levels of the chemical butadiene were detected. Schools in the area have also canceled classes for the rest of the week.

Jefferson County emergency management officials said the elevated levels did not pose a serious health risk, but could cause dizziness, nausea, headaches or irritation to the eyes and throat.

Butadiene is a chemical used to make synthetic rubber and other products.

The first explosion happened early November 27 at the TPC Group plant about 80 miles east of Houston and was so powerful it shattered windows and ripped doors off hinges of nearby homes. A second blast occurred about 13 hours later, and the fire wasn’t contained until Nov. 29.

The blast sent a huge plume of smoke into the air that was visible for miles.

The explosion was the latest in a series of high-profile accidents this year up and down the Texas Gulf Coast, which is home to the highest concentration of oil refineries in the nation. In July, an explosion at an ExxonMobil refinery in Baytown left more than dozen people with minor injuries and put nearby residents under a shelter-in-place advisory for three hours.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)