Olivia Munn, Marlee Matlin, Eliza Dushku, Jordin Sparks and Nikki Sixx are among the stars who have expressed their condolences to the families of the 19 firefighters who were killed by a blaze in Arizona on Sunday (30Jun13).

The emergency workers died while battling a fast-moving wildfire, which was sparked by a lightning strike, close to the town of Yarnell in central Arizona.

The 19 men were part of the Granite Mountain Hotshots, a specialist team of wildfire fighters, and news of the tragedy has hit headlines around the world, prompting an outpouring of sadness from a number of celebrities.

Motley Crue rocker Sixx was among those who reached out to the families who lost loved ones in the blaze, hailing the firefighters as "heroes".

In a post on Twitter.com, he writes, "So sad to hear about the 19 firefighters who lost their lives today in AZ (Arizona). Our prayers go out to the families and community. Heros (sic)."

Arizona native Sparks adds, "My heart & prayers are with Az tonight. So tragic. Yarnell Firefighters," and actress Munn writes, "Tragedy in Arizona. My thoughts & prayers are with all the loved ones of the 19 fallen firefighters.

Marlee Matlin concurs, "Thoughts and prayers go out to families of the 19 firefighters killed in Arizona wildfire. Such a tragedy" and Dushku sends "love & prayers" to those affected, along with Melissa Joan Hart: "Praying for the firefighters that passed away and those still fighting the fires in Az."

U.S. President Barack Obama, who is currently on an overseas trip to South Africa, also honoured the men in a statement, which reads, "Yesterday, 19 firefighters were killed in the line of duty while fighting a wildfire outside Yarnell, Arizona. They were heroes - highly skilled professionals who, like so many across our country do every day, selflessly put themselves in harm's way to protect the lives and property of fellow citizens they would never meet."