An outbreak of COVID-19, resulting in 77 positive cases, has been traced to a youth basketball tournament held last month in California's Santa Clara County, public health officials said Friday.

At the tournament, held Nov. 7 and 8 at Courtside Basketball Center in Placer County, were 39 middle school and high school players, three coaches and 35 “additional contacts.”

Officials said it violated local and state orders for youth sports put in place during the coronavirus pandemic.

Another 17 cases outside the county have also been traced to the event, officials said in a news release.

“This outbreak is a troubling reminder that the widespread prevalence of COVID-19 in our community threatens all of us, and does not limit itself to geographic boundaries,” Dr. Monika Roy, Santa Clara County’s assistant public health officer, said in a statement.

“Public Health orders, directives, and guidance around contact sports and sporting events are in place for a reason. The risk of transmission in these settings can easily result in community spread that threatens the most vulnerable among us.”

The California Department of Public Health is investigating the incident, according to the news release, and Courtside’s website said the center is closed until further notice “out of precaution with the statewide lockdown and for the safety of all.”

The outbreak comes as California is seeing record numbers of COVID-19 cases during the holiday season.

FedEx took to Twitter Friday night to announce that it's on track to start delivering Pfizer's COVID-19 vaccine, which was given emergency use authorization by the Food and Drug Administration Friday.

“We’re in motion to begin delivering our first shipment of COVID-19 vaccines from @pfizer -@BioNTech_Group to communities across the U.S.,"FedEx tweeted.

In a press release, the transportation company -- which has more than 90 cold chain facilities across five continents -- said it will use its FedEx Priority Overnight service to get vaccines to dosing centers around the country, and soon, the world.

"Vaccine distribution will be balanced among major cargo carriers, and FedEx is working closely with healthcare customers to prepare for additional vaccine shipments and transportation of critical vaccine-related supplies," they said in their statement.

Mexico approved emergency use of Pfizer and BioNTech's COVID-19 vaccine on Friday.

The announcement came shortly before the U.S. Food and Drug Administration said that it had authorized Pfizer's vaccine. Mexico has recorded over 1.2 million cases and 113,000 deaths -- fourth-most globally behind the U.S., Brazil and India.

The United Kingdom, Bahrain and Canada have also authorized the vaccine.

The U.S. Food and Drug Administration has authorized Pfizer and BioNTech's COVID-19 vaccine for emergency use.

President Donald Trump announced the news on Twitter.

The move comes a day after the FDA's advisory committee recommended that the U.S. government authorize the nation's first COVID-19 vaccine for people over the age of 16.

The first vaccine will be administered in less than 24 hours, Trump said Friday night.

Health and Human Services Secretary Alex Azar told "Good Morning America" Friday morning that up to 20 million Americans will be vaccinated this month.

The chief science adviser to Operation Warp Speed, the U.S. government's initiative to expedite vaccine development, said he doesn't know what vaccine-related executive order President Donald Trump is expected to sign on Tuesday.

"Frankly, I don't know and, frankly, I'm staying out of this. I can't comment," Dr. Moncef Slaoui told ABC News chief anchor George Stephanopoulos in an interview Tuesday on "Good Morning America."

When pressed on the matter, Slaoui added: "Our work is, you know, rolling. We have plans. We feel that we can deliver the vaccines as needed, so I don't exactly [know] what this order is about."

Trump is expected to discuss the order at a COVID-19 vaccine summit to be held at the White House later Tuesday, multiple White House officials told reporters during a background briefing on Monday evening. While it's not entirely clear on how exactly the order would work, the move is designed to prevent the U.S. government from shipping any vaccine doses it has purchased to aid foreign countries until all the needs within the United States are met.

White House officials also denied reports that the Trump administration turned down an offer last summer to purchase an additional 400 million doses of a COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech, and that the companies now may not be able to provide more of their vaccine to the United States until June 2021 because they have committed those doses to other countries.

When asked about the matter, Slaoui explained Operation Warp Speed's strategy in securing vaccine doses.

"We selected six different vaccines to build a portfolio to manage the risk that some may work and some may not work, but also to ensure that as more than one would work that we would accumulate vaccine doses from this portfolio of vaccines," he said. "If somebody came to us and said, let's buy more of this vaccine or that vaccine, no one reasonably would buy more from any one of those vaccines because we didn't know which one would work and which one may be better than the other. Once the vaccine's performance becomes known is the right time, given the strategy we've taken, to go and order more vaccine doses, which we may be doing. And frankly, the constructive thing to do if one of the suppliers has challenges producing enough vaccine doses is to roll our sleeves and help ensure that capacity can be increased."

Slaoui said he's confident the U.S. government will be getting vaccines to Americans who need them "as soon as possible" and that plans are "still on track."

"We will work with Pfizer to try and increase capacity and have those vaccines available," he said. "We have two more vaccines from J&J and AstraZeneca that will be completing their Phase 3 trials in January and most likely, I hope, be approved for use in February. We have tens of millions of doses from those vaccines, you know, participating to the volume of vaccines we need to immunize the U.S. population as we promised, all of it by the middle of the year 2021 and that's still on track."

Slaoui said Operation Warp Speed has a meeting with President-elect Joe Biden's transition team scheduled for Thursday.

"We look forward to, you know, sharing all the information and working together," he said. "Our objective has always been outside of politics and making sure we make available these vaccines for the U.S. people, and that's what we're doing."

ABC News' Ben Gittleson, John Parkinson and Eric Strauss contributed to this report.