About 40 people were wounded in an explosion at a rally in Karachi on Wednesday, according to reports in the Pakistani media.

The blast was caused by a “cracker” tossed near the hardline Jamaat-i-Islami group’s rally by unidentified people on a motorcycle, a report on the Geo News website said. It said the attackers managed to escape.

East senior superintendent of police Sajid Sadozai said two unidentified persons riding a motorcycle threw an RGD-1 grenade at the rally and fled, another report on the Dawn website claimed.

One person was stated to be critical while no deaths were reported yet, the Dawn quoted Meeran Yousuf, the media coordinator for the Sindh health minister, as saying. He had earlier ruled out that the blast was caused by a planted bomb, the report said.

The incident happened near a mosque and shattered windows of cars nearby. A heavy contingent of security forces reached the site after the incident.

Eyewitnesses said the blast caused a stampede and severely injured five people on the site, according to the Geo News report. “The banned Sindhudesh Revolutionary Army (SRA) claimed responsibility for the attack through social media,” the Dawn said.