Sum 41 have announced their South American tour with Four Year Strong, Attack Attack!, and Pierce The Veil has been canceled due to Deryck Whibley's ongoing medical condition. Whibley, frontman for Sum 41, suffered from a back injury during the Boise, Idaho stop of the 2011 Vans Warped Tour. Statements from both Four Year Strong and Sum 41 can be seen below.

Sum 41's official statement:

Sum 41 has indefinitely postponed the remainder of dates on their Screaming Bloody Murder tour for 2011 due to a medical condition Deryck Whibley is currently undergoing treatment for. In order to fully recover, Deryck is under doctor's orders to start a rehabilitation program and to recuperate for the rest of 2011. This will make the cancelation of all upcoming tour dates beginning in South America September 4th through Asia October 18th necessary.

"We are all devastated that our best tour yet has been interrupted." said Drummer Stevo Jocz " Our band lives to be on stage and playing in front of our fans. We never want to let anyone down but the most important thing right now is that Deryck makes a full recovery so we can continue on next year . We’re working as fast as we can to reschedule these dates."

The following dates have been canceled:

9/4/2011 Mexico - Sala de Armas

9/6/2011 Santiago, Chile - Caupolican

9/8/2011 Curitiba, Brazil - Master Hall

9/9/2011 Rio de Janeiro, Brazil - Fundicao Progresso

9/10/2011 Sao Paulo, Brazil - Via Funchal

9/11/2011 Buenos Aires, Argentina - Estadio Cubierto Malvinas

9/16/2011 Paris, France - Fete de l'Humanite Festival

9/17/2011 St. Nolff, France - Festival de ST Nolff

10/6/2011 Jakarta, Indonesia - Karnaval Beach

10/8/2011 Sri Petaling, Kuala Lumpur - Rockaway Fest

10/10/2011 Taipei, Taiwan - Taipei University Auditorium

10/12/2011 Shanghai, China - Shanghai Grand Stage

10/14/2011 Beijing China - Wukesong Indoor Hall

10/16/2011 Manila - A Venue Hall

10/18/2011 Bali - Hard Rock Cafe

Ticket refunds will be available at the point of purchase.

Please check back to Sum for information on rescheduling and upcoming touring in 2012.

Four Year Strong's official statement:

We’re heartbroken to say that our upcoming tour with Sum 41 in South America just got cancelled. We just found out our friend Deryck Whibley from Sum 41 needs focus on recovering from a medical condition. Health comes before anything else, especially when bands spend so much of their time out on the road. We wish him all the best and we’re working hard to get back on the road as soon as possible, we wish this was in our hands and hope to see you soon