London, July 11 (Inditop.com) Fans of pop star Britney Spears are worried about her health again after she collapsed during a recent rehearsal on the European leg of her Circus world tour.

The “Toxic” hitmaker was practising a dance routine for a new song when she keeled over, suffering a bruise to her chest, reported IANS-WENN.

“She collapsed when the dancers went to put her back on her feet. She fell to the floor and landed on one of the dancers’ legs,” said a source.

“The dancer’s tennis shoe smacked Britney in the chest and on the face. It hit her chest with such a force that it caused a four-inch bruise,” added the source.

It was reported that Britney’s hectic tour schedule and a low blood-sugar level were responsible for the incident.