No Covid cases were detected on Wednesday, a first for the Games.

With nearly 70,000 people inside Beijing’s “closed loop” taking Covid tests every day, not a single case was detected on Wednesday, the first day of the Games that was entirely free of new cases.

It was the clearest sign yet that the mammoth efforts to prevent an Omicron outbreak among foreign visitors had been successful, with three days remaining until the closing ceremony. China has gone to great lengths to prevent athletes and visitors from mixing with the general population and has placed stringent requirements on entry to the country.

Upon arrival, all visitors — a group that includes athletes, team officials and journalists — are required to undergo polymerase chain reaction tests and isolate in hotel rooms until results come back a few hours later. Those who test negative are allowed to move freely within the Games’ so-called closed-loop system, which restricts athletes and others involved with the Olympics to designated hotels and venues.

All Olympic attendees undergo a P.C.R. test each day. On Wednesday, all 68,970 people inside the loop tested negative, as did the seven people who arrived at the airport.

The pace of positive tests had slowed to a trickle this week, with two on Tuesday and one on Monday. Those who test positive but do not require medical treatment must isolate in hotel rooms until they register two negative tests.