Room reservations and sportsbooks were still dark across swaths of Las Vegas on Friday as the community trudged through its fifth day of a battle against hackers who struck the city’s biggest hotel chain.

As of 1 p.m. PDT, visitors to the "book a room" tab on the MGM Resorts website were greeted with the stark message of "online hotel reservations are currently unavailable."

The site also told guests that any change and cancellation fees are being waived for stays between Wednesday and Sunday.

The security breach also threatened to dim sports betting, a key attraction for football-minded Las Vegas visitors every fall. The machines used to take wagers were flickering on and off Friday at properties throughout the chain.

"They can take bets, kind of. It's in and out," influencer Jennifer Gay, who runs the popular vegasstarfish Instagram feed, said from the Bellagio sportsbook Friday. "If the system is up, you can (bet). When it's down, you can't."

She added: "The real gamble is whether you can wager on a game or not."

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A spokesperson for MGM could be immediately reached via email or phone Friday.

The major chain includes some of the city’s most famed properties such as MGM Grand, Bellagio, Mandalay Bay, ARIA, The Cosmopolitan of Las Vegas, Four Seasons, Luxor, New York-New York and Delano.

MGM employees were unable to access their corporate emails as of Friday morning, a worker who was not authorized to speak for the company told NBC News.

The hacking group claiming responsibility reportedly used a decidedly low-tech tool, the telephone, to call into an IT help desk and claimed to be an employee to gain access to MGM systems.

"In terms of technology mishaps, failures that are due to technology, this is by far the worst" incident in Las Vegas since a famed 2004 power failure at the Bellagio, said Mehmet Erdem, a professor of hotel operations and technology in UNLV’s College of Hospitality.

"If it's indeed true that somebody got tricked over the phone at the help desk, that should not have happened. I know for a fact there's training that you have to confirm the source. If you get a call from someone saying they're 'Mehmet,' you have to call me back at my office number. There are many simple steps, a few questions to be asked."

Despite the ongoing struggle, bar owner Noel Bowman said the situation Friday was much improved from earlier in the week. Now only a few darkened slot machines dot casino floors on MGM properties.

"It's now a minor inconvenience," said Bowman, owner of he Minus5 Ice Bars. "Day 1 was a little bit of chaos."

Bowman and Gay both heaped praise on MGM workers, from executives to the labor food chain, for keeping check-in lines moving, performing manual tasks ordinarily done digitally and answering guest questions throughout this challenging week.

"If you're a guest and this is your first time at Bellagio, you might not realize there's an issue. That's how good they're doing," Gay said.

"The back of the house is a mess. There's no email, there's no employee log-on. I mean, the way they are transferring messages is Bob is walking from Spago to the cage to tell them he needs money."