SANTA CLARA, Calif. -- The San Francisco 49ers, already reeling from injuries, placed four players on the reserve/COVID-19 list on Wednesday and declared all four of them out for Thursday night's home game against the Green Bay Packers.

A league source told ESPN's Adam Schefter that wide receiver Kendrick Bourne tested positive for COVID-19, a result he received Wednesday morning after taking the test on Tuesday. Bourne was placed on the reserve/COVID-19 list early Wednesday afternoon as the league and the 49ers conducted additional contact tracing.

Early Wednesday evening, the 49ers announced that left tackle Trent Williams and wideouts Brandon Aiyuk and Deebo Samuel also were going on the reserve/COVID-19 list, and they ruled Aiyuk and Williams out for Thursday's game. Samuel already had been ruled out because of a hamstring injury.

Williams, Aiyuk and Samuel were all deemed close contacts of Bourne, a league source told ESPN, which is why they landed on the reserve list. According to NFL rules, players who are considered high-risk close contacts must remain on that list for at least five days and continue testing.

Despite all of that, Thursday's contest versus Green Bay is expected to go on as scheduled, according to multiple league sources. The Packers departed Green Bay at around 4:30 p.m. CT Wednesday and were scheduled to arrive in the Bay Area around 6:30 p.m. PT.

The 49ers held a walk-through, meetings and a practice Tuesday evening in preparation for Thursday's game. Upon learning of Bourne's positive test Wednesday morning, the 49ers closed their facilities and entered the NFL's intensive protocol. All team activities were conducted virtually on Wednesday, and players and staff took part in drive-through COVID-19 testing.

"The health and safety of our players, staff and community are the organization's highest priority," the 49ers said in a statement. "We will continue to work closely with the NFL and medical professionals and will follow their direction."

The loss of Bourne, Aiyuk and Williams only adds to an extensive list of key 49ers who will not be available against the Packers. The team has been hit particularly hard at wide receiver, where it will be missing Bourne, Samuel and Aiyuk in addition to Dante Pettis, whom they released Tuesday and the New York Giants claimed on Wednesday.

The only healthy wideout on San Francisco's roster at the moment is Trent Taylor, though Richie James could return from an ankle injury and is listed as questionable. The team is expected to elevate WRs Kevin White, River Cracraft and Chris Finke from the practice squad and could activate tight end Jordan Reed, who was limited in practice this week, from injured reserve. Justin Skule will step in at left tackle for Williams.

In addition to the four players added to the COVID-19 list, the Niners also will be without quarterback Jimmy Garoppolo (ankle), tight end George Kittle (foot) and running backs Tevin Coleman (knee), Raheem Mostert (ankle) and Jeff Wilson Jr. (ankle). That group has combined to make up 71% of the team's scrimmage yards this season, according to ESPN Stats & Information research.

Thursday's game against Green Bay is the first meeting between the teams since the NFC Championship Game on Jan. 19. In that game, seven 49ers had an offensive touch in Mostert, Coleman, Garoppolo, Samuel, Bourne, Kittle and running back Matt Breida, who was traded to the Miami Dolphins in the offseason. None of them will be in uniform for the Niners on Thursday night.

The Packers, meanwhile, will be without running back AJ Dillon, who tested positive for COVID-19 on Monday, while running back Jamaal Williams and linebacker Kamal Martin have been ruled out after they were also deemed high-risk close contacts of Dillon.