Story highlights

NEW: Many of the dead are police and security officers, authorities say

More explosives detonate as security forces investigate two earlier blasts

67 are wounded and at least 19 are killed, police say

Baghdad CNN —  

At least 19 people were killed and 67 others were wounded Thursday in three explosions in the southern Iraqi city of Basra, two police officials said.

A roadside bomb and a motorcycle exploded in quick succession in a busy commercial district that includes shops and restaurants, the officials said.

When curious onlookers and Iraqi security forces arrived to the scene to investigate, another motorcycle rigged with explosives detonated, causing most of the casualties, police said. A number of Iraqi police and army security officers were among the dead, the officials said.

The oil-rich, predominantly Shiite city of Basra is about 500 km (310 miles) south of Baghdad.