The top three seeds in the women's draw of the Abierto Mexicano Telcel won their second-round matches in Acapulco on Wednesday.
Number one seed Dominika Cibulkova was a 7-5 6-2 winner over Yanina Wickmayer, while Canada's Eugenie Bouchard (two) beat Lara Arruabarrena by the same scoreline.
Third seed Kaia Kanepi was pushed harder by Julia Goerges of Germany before sealing a 6-7 (4/7) 6-4 7-6 (8/6) triumph.
One seed did fall though - Bojana Jovanovski of Serbia slipped to a 6-1 6-4 loss against New Zealand's Marina Erakovic.
There were also wins for Zhang Shuai, Ajla Tomljanovic, Christina McHale and Caroline Garcia.