A bomb attack in Pakistan's Karachi on Sunday killed at least 45 people, the city's top official said.
Hashim Raza Zaidi said the death toll could rise further, as about 150 others were wounded in the blast, many of whom remain in a critical condition.
GlobalPost's Mariya Karimjee, reporting from the southern Pakistani city, said the blasts left the area in ruins. "Took place in a Shiite neighborhood," she said. "Two buildings collapsed. People [are] stuck in the rubble."
Government official Taha Farooqi said rescue efforts are ongoing. He also said more wounded people may be trapped underneath fallen buildings, reported the Associated Press.
Local police official Azhar Iqba told AP that the Shiite mosque was targeted as people were leaving from evening prayers, and women and children were among the victims. Top police official Shabir Ahmad Sheikh described it in comments to Reuters as "a powerful blast on a congested Shi'ite-dominated area."
It was not immediately clear what caused the explosion, with police telling AP they first thought it was a motorcycle suicide bombing but now believe additional bombs may have been planted in the area.
Attacks against Pakistan's large Shiite community have been on the rise. Between 17 and 26 million Shias are estimaged to live in the country, representing some 10 to 15 percent of the nation's Muslim population, according to PEW.
Agence France-Presse contributed to this report.