People gather around the site of an explosion at a restaurant in Jhabua district in the central Indian state of Madhya Pradesh on September 12, 2015. At least?60 people were killed when a gas cylinder exploded in a restaurant. [Photo/CFP]

NEW DELHI - At least 85 people were killed when a cooking gas cylinder blew up in a crowded restaurant in central India on Saturday, triggering a second blast of construction detonators stored illegally nearby, police said.

The explosions tore through the restaurant as people sat down for breakfast during the morning rush hour in the town of Petlawad, about 800 km (500 miles) south of New Delhi, Inspector B.L. Gaur told Reuters.

Gaur said people who had gathered outside the restaurant after the initial blast were caught in a second explosion when gelatin sticks stored in a nearby building caught light, blew up and buried scores of people as the roof caved in.

"When the first blast took place in the gas cylinder many people collected there to watch and see what had happened. Then there was a secondary blast," Gaur said, adding the explosion was so powerful it damaged adjacent buildings and ripped out nearby windows.

Bodies lay amid the rubble of the collapsed restaurant and twisted motorcycles and debris were strewn outside, as a crowd of onlookers searched for survivors.

Around 100 people were also injured in the blast, Arun Sharma, a local medical officer, said.

Police said the death toll had risen throughout the day as rescue workers continued to pull bodies from under the rubble. The accident is one the deadliest to hit India in recent years.

"This is a tragic incident, which has shook me. The causes of the incident will be investigated," Madhya Pradesh's chief minister Shivraj Singh Chouhan told local television channels.

Chouhan has announced 200,000 rupees ($3,000) in compensation for the families of those killed and 50,000 for those injured, media reported.

Gaur said the detonators, which are used for construction activity and digging wells, should not have been kept in the room near to the restaurant.

($1 = 66.2310 Indian rupees)