ISMAILIA, Egypt, April 24 (Reuters) - A fire broke out in a clothing factory in the Egyptian town of Ismailia on Thursday, causing damage estimated at about $20 million.

Twenty workers were taken to hospital after inhaling smoke, medical sources said.

The fire department has sent four helicopters and more than 30 fire trucks to fight the fire in an industrial area of the town, 120 km (75 miles) northeast of the capital Cairo.

The fire broke out in a fabric storage room and spread to the rest of the factory, security sources said. The cause of the fire is still unknown. (Reporting by Yusri Mohamed, writing by Aziz El-Kaissouni) (aziz.el-kaissouni@reuters.com; +20 2 2578 3290/1; Reuters Messaging: aziz.el-kaissouni.reuters.com@reuters.net))