The first medals were won on the opening day of the event in Pachuca ©COPACI

American Leah Thomas and Colombian Brandon Smith won the women's and men's time trial races, respectively, on the opening day of the Pan American Road Cycling Championships in Mexico.

Thomas led a one-two for the United States in the women's event, completing the 22 kilometres course in 28min 19.883sec to beat compatriot Amber Neben in Pachuca.

The bronze medal was claimed by Constanza Paredes of Colombia.

In the men's race, contested over 33km, Smith crossed the line in 54:10.321 to take gold.

The Colombian was more than 27 seconds faster than nearest challenger José Rodriguez of Chile, who finished in 54:37.988.

Ignacio de Jesús Prado delivered a medal for the host nation as he earned bronze in 55:27.804.

Leah Thomas of the United States clinched the women's time trial title ©Getty Images
Leah Thomas of the United States clinched the women's time trial title ©Getty Images

Teniel Campbell of Trinidad and Tobago triumphed in the women's under-23 race by clocking 30:40.63.

Campbell crossed in front of Costa Rica's Jennifer Morales and Cuba's Jeydy Pradera, who won silver and bronze, respectively.

Diego Ferreyra of Chile secured gold in the men's under-23 event in 41:10.375, with Alexis Benjamín Quinteros of Ecuador earning silver.

Ferreyra's team-mate Alejandro Lovera was the recipient of the bronze medal.

Action resumes on Friday (May 3) following the Pan-American Cycling Confederation Congress tomorrow.