"A female suicide bomber walking among Shiite pilgrims in northern Baghdad detonated an explosives belt on Monday, killing at least 41 people and wounding more than 100," the Associated Press reports.

The BBC adds that the pilgrims "were marking Arbaeen, the end of 40 days of mourning for the death of Prophet Muhammad's grandson. ... In recent years the pilgrimage has been the target of similar attacks, blamed on Sunni extremists."

Update at 10:15 a.m. ET: The AP says Iraqi officials now report the death toll has risen to 54. We've updated the headline on this post as well.

Update at 8:20 a.m. ET. From Baghdad, NPR's Lourdes Garcia-Navarro reports that police say the bomber blew herself up at a rest stop where pilgrims were getting food and water. She adds that even though there has been a deadly series of attacks in recent days, official figures show that "civilian casualties have been declining" in recent months: