Top seed Angelique Kerber advanced to the round of 16 at the Miami Open and she was joined by Simona Halep.
World number one and two-time grand-slam champion Kerber defeated American Shelby Rogers in straight sets on Sunday.
Romanian third seed Halep eased past Anett Kontaveit at the WTA Premier tournament.
Veteran Venus Williams moved into the last 16 with a straight-sets victory over Patricia Maria Tig.
KERBER CONQUERS ROGERS
The German star overcame a stern test from Rogers, winning 6-4 7-5.
Kerber recovered from breaks in both sets, tallying 17 winners and 22 unforced errors to book her spot in the fourth round, while Rogers posted 51 unforced errors.
Next up for Kerber is Japanese qualifier Risa Ozaki, who stunned Julia Goerges 7-6 (7-5) 6-3.
HALEP BLITZES HER WAY INTO LAST 16
The Romanian wasted no time progressing to the next round with a 6-3 6-0 win against Kontaveit.
Halep needed just 56 minutes to dismantle the Estonian.
She did not face a break point and converted five of her own in Sunday's late match.
Standing in the way of Halep and the quarter-finals is Samantha Stosur after the 14th seed outlasted Peng Shuai 4-6 6-3 7-5.
VENUS ROLLS ON
Williams and her bid for a fourth Miami Open crown remains on track following her 6-3 6-0 rout of Maria Tig.
The 11th seed - making her 18th appearance at the event - dropped just five points on her first serve to power in the next round.
It gets a tougher for Williams in the last 16 as former world number two Svetlana Kuznetsova awaits.
Russian seventh seed Kuznetsova accounted for Taylor Townsend 6-4 6-2.
Johanna Konta progressed from the third round but fellow seed Madison Keys was not so fortunate.