Carlos Santana collapses during concert in Michigan

The guitarist collapsed onstage at Pine Knob Music Theatre (formerly DTE Energy Music Theatre), an outdoor amphitheater in Clarkston, about 40 miles northwest of Detroit

At approximately 10pm ET, Billboard's Gary Graff tweeted that Santana was being treated

Roup Raj, an evening anchor and reporter for Fox2 Detroit, retweeted a photo of what appears to be Santana receiving medical attention

"The crowd asked for prayers for him due to a 'serious medical issue'," 

Santana was taken offstage on a stretcher 20 minutes after collapsing at Pine Knob Music

No word on his condition yet, but he waved as he was rolled off

Santana had suffered from heat exhaustion and dehydration, and was taken to McLaren Clarkston for observation, explains his rep, Michael Vrionis

The Pavilion at Star Lake in Burgettstown, PA, where Vrionis was scheduled to perform Wednesday evening, has been rescheduled for a later date, according to Vrionis