A powerful blast Monday at a northern Indian paper factory sparked a blaze, killing nine workers and leaving hundreds trapped, police said.

At least 50 others were injured in the blast and fire at the factory in the town of Udham Singh Nagar in India's Uttaranchal state, said police official Amit Kumar Sinha.

"The blast took place in the factory when hundreds of workers were working in the evening shift. The whole area caught fire after the blast," Sinha said by telephone. "So far nine bodies have been recovered. The toll may go up."

The town is about 400 kilometers (245 miles) northwest of the region's largest city, Lucknow.

CountryWatch: India