The City of Dallas will undergo aerial spraying again tonight for mosquitoes, weather permitting, in an effort to stop the spread of West Nile virus throughout the area.

The spraying will occur for Preston Hollow and other Dallas neighborhoods between 9 p.m. and 1 a.m. Monday, according to the City.

The second round of spraying will take place to kill new mosquitoes born since the last round. 

Crews with the Centers for Disease Control are in Dallas County to observe and learn from the spraying operation, WFAA-TV (Ch. 8) reported on its website. The county doesn't have any new data from the West Nile virus traps, but it's expecting additional information from trapped mosquitoes sometime in the next 24 hours.  

Dallas County Judge Clay Jenkins, who declared an emergency, told the station that preliminary results show the chemical is working.

"What we're seeing from the test so far is a decrease in the West Nile virus carrying activity mosquitoes in the traps," he said.

To find out more information about West Nile virus and what is being done to prevent it from spreading, visit the City of Dallas website.