Two people died in what officials believe was a mass fentanyl overdose over the weekend involving five people in a hotel room in the Hawaii tourist mecca of Waikiki.

Emergency responders were called to the Outrigger Reef Waikiki Beach Resort on Sunday morning and found five people. A 44-year-old man was pronounced dead at the scene, while two men, ages 40 and 53, were taken to a hospital in critical condition. Two women, 53 and 47, were transported in serious condition.

Honolulu police said the 53-year-old man later died at the hospital. Police said fentanyl was found at the scene.

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Outrigger spokesperson Monica Salter told the Honolulu Star-Advertiser the resort is working with authorities and was unable to share guest information for privacy reasons.

Fentanyl is an opioid painkiller many times more powerful than heroin, and typically is prescribed to treat severe pain. It frequently appears as an illegal street drug mixed with other substances, such as heroin.

Experts say the growing prevalence of fentanyl in the illicit drug supply is a top driver of the increasing number of overdose deaths in the U.S.

It's a growing concern across Hawaii. In May, police on the Big Island became the first department in the state to release fentanyl statistics. The statistics showed that during the first four months of this year, Hawaii Police Department officers made 22 fentanyl arrests and recovered 383.02 grams of fentanyl and 598 fentanyl pills.