[UPDATE BELOW] Aerosmith cancelled a performance in Concord, California last night just hours before show time, and now there’s speculation that the band’s tour could be postponed even further. An official statement from Aerosmith said that the Concord show was cancelled due to “illness” without much further elaboration, but TMZ reported that drummer Joey Kramer had heard complications that could require surgery.

Aerosmith’s Let Rock Rule tour currently has ten dates left until its conclusion on September 12th. The band were already forced to cancel a handful of dates in Ukraine because of the unrest in the region. The band themselves have refused to comment on the cancellations.

Aerosmith are no strangers to health issues. Bassist Tom Hamilton missed the band’s 2006 tour while recovering from tongue and throat cancer (he left another tour in 2013 due to an unspecified illness.), and Steven Tyler injured his shoulder onstage in 2009. Rhythm guitarist Brad Whitford had to miss dates on the same tour after suffering a head injury that required surgery.

[UPDATE] The band have issued a press release stating that the Let Rock Rule tour will resume on Saturday, August 16th. They also confirmed that Kramer underwent minor heart surgery, but denied TMZ’s assertions that Kramer had a history of heart trouble. Kramer issued the following statement. “I’m feeling better than ever and I’ll be back sitting in the best seat in the house, hitting it harder than ever for our amazing fans. My gratitude and thanks for all the love and support showered on me during this time.”