A former basketball and softball coach at Azle High School has been charged with sexual assault of a child, police said.

Carlos Font-Santiago, 32, was arrested by the Tarrant County Sheriff's Office on Dec. 12. He was previously arrested in April for an improper relationship between an educator and a student, authorities said late Friday. 

Azle police said the assault charge is an updated charge after a "lengthy investigation into Font-Santiago's improper relationship with a former student."

"At the time of the offense, Font-Santiago was employed at Azle High School, where he coached basketball and softball," Azle police said in a news release. 

The investigation is ongoing.