(RollingStone.com) -- U2 have postponed their much-anticipated tour behind How to Dismantle an Atomic Bomb, originally scheduled to kick off March 1st in Miami. "All of the plans are in total flux," a source close to the band told Rolling Stone, citing a family illness as the reason for the change. Tour dates were to be announced and go on sale this month, but those plans have been delayed.

The band, which is nominated for three Grammys for the single "Vertigo," still intends to play the February 13th awards ceremony in Los Angeles and to attend its induction into the Rock & Roll Hall of Fame on March 14th in New York. However, a new timeline for the tour has not been set.

According to longtime tour designer Willie Williams, the tour's stage and video screens are in the process of being built. "We are developing some new technologies to deliver visual content," he told Rolling Stone.

U2's last world tour, in support of All That You Can't Leave Behind, made them the top-grossing act of 2001.