ST. LOUIS, Mo. – Several loud booms shook southern portions of the St. Louis area today. The blasts happened periodically throughout the day and it was initially not clear why they were happening.

On the Illinois side, the St. Clair County Office of Emergency Management sent a warning Wednesday that the noises would be coming from a construction project from 8:45 am until 9:00 am today. The sustained booms were actually coming from an unrelated project on the other side of the Mississippi River.

Ameren has been working on building new 294-foot-tall power transmission towers across the Mississippi River over the past few weeks. A helicopter has been helping crews string transmission lines.

“Today we completed the implosion of two Ameren Transmission towers near the Mississippi River. The new towers will bring increased reliability and resiliency to the electric grid. This project benefits hundreds of thousands of electric customers in the Metro South area,” states Ameren.

A FOX 2 photographer found a transmission tower on the ground near the River City Casino site. They are demolishing two old massive energy towers in Illinois and Missouri.

The first test blast happened at around 9:00 am. The second occurred at 1:00 pm and took down the Illinois tower. The last blast was scheduled shortly before 3:00 pm and dropped the Missouri tower.

Ameren said it notified the St. Louis Mayor’s Office director of operations and communications team as well as the directors of streets, the director of public safety, and the Board of Public Service.

The company said it also contacted officials in St. Clair County, including the mayors of Dupo, East Carondelet, Cahokia, and the St. Clair County Emergency Management Agency. Ameren said St. Louis County police were on-site on the Missouri side, and St. Clair County police were on-site in Illinois.