Unruffled by a bomb scare that locked down the Sony Open late on Tuesday, world number one Rafael Nadal brushed past Italy's Fabio Fognini 6-2, 6-2 to join Novak Djokovic, Roger Federer and Andy Murray in the last eight.

Officials announced a suspicious package had been left near the main entrance to the sprawling tennis facility which was quickly locked down, keeping thousands of spectators from entering or leaving while Miami Dade police investigated.

The all clear was given just before Nadal stepped onto the Crandon Park centre court to face Fognini in the final match of the night. The Spaniard showed no signs of being alarmed by the bomb scare as he completed the win in 62 minutes. "Every day I have to try to find my rhythm, try to think about myself, what I have to do well, so I just try to be focused on what I really need to do to play well," said Nadal.

Nadal's next opponent is Canadian Milos Raonic, who beat Benjamin Becker 6-3, 6-4.Nadal's great rival Federer was also in cruise control,  needing just 49 minutes to dismiss ninth seeded Frenchman Richard Gasquet 6-1 6-2.

Defending champion Murray, playing his first event since splitting with coach Ivan Lendl last week, has looked increasingly comfortable and confident on his own. He disposed of 11th-seeded Frenchman Jo-Wilfried Tsonga 6-4 6-1 without facing a single break point.Djokovic, a three-time winner on the Miami hardcourts, had only two break points the entire match but that was all the second seeded Serb needed, converting both chances on his way to a 6-3 7-5 win over  Spaniard Tommy Robredo.

Not everything at Crandon Park tennis center went according to script, however, as Japan's Kei Nishikori and Ukraine's Alexandr Dolgopolov pulled off a pair of fourth-round upsets.

Dolgopolov battled to a 6-4 3-6 6-1 win over Swiss third seed and Australian Open champion Stanislas Wawrinka, while Nishikori shocked fourth seeded Spaniard David Ferrer 7-6(7) 2-6 7-6(9).

In other fourth-round action, big-hitting Canadian Raonic blasted German lucky loser Becker 6-3 6-4, while another big-hitter, towering American John Isner, was beaten 6-3 7-5 by Czech seventh seed Tomas Berdych.

Serena packs off KerberIn the women’s event, defending champion Serena Williams closed in on a seventh Sony Open title with a 6-2 6-2 quarterfinal demolition of German Angelique Kerber.

Williams' win sets up a semifinal rematch of last year's final against Maria Sharapova, a five-time runnerup on the Miami hardcourts, who advanced with an equally impressive 7-5 6-1 win over eighth-seeded Czech Petra Kvitova. Sharapova, who has come up short in the Miami final each of the last three years, dropped her opening serve to Kvitova but that would be the only time in the entire match.

The fourth-seeded Russian took control with a break to get back on level terms at 4-4 and then again to close out the first set. Sharapova then dominated the second set, storming through the first five games before a reeling Kvitova held her serve.